Metal utilization in supported, metal-containing catalysts

ABSTRACT

Generally, the present invention relates to improvements in metal utilization in supported, metal-containing catalysts. For example, the present invention relates to methods for directing and/or controlling metal deposition onto surfaces of porous substrates. The present invention also relates to methods for preparing catalysts in which a first metal is deposited onto a support (e.g., a porous carbon support) to provide one or more regions of a first metal at the surface of the support, and a second metal is deposited at the surface of the one or more regions of the first metal. Generally, the electropositivity of the first metal (e.g., copper or iron) is greater than the electropositivity of the second metal (e.g., a noble metal such as platinum) and the second metal is deposited at the surface of the one or more regions of the first metal by displacement of the first metal. The present invention further relates to treated substrates, catalyst precursor structures and catalysts prepared by these methods. The invention further relates to use of catalysts prepared as detailed herein in catalytic oxidation reactions, such as oxidation of a substrate selected from the group consisting of N-(phosphonomethyl) iminodiacetic acid or a salt thereof, formaldehyde, and/or formic acid.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/557,700, filed Jul. 25, 2012, which is a continuation of U.S. patentapplication Ser. No. 12/434,360, filed May 1, 2009, now issued as U.S.Pat. No. 8,252,953, which claims the benefit of U.S. ProvisionalApplication Ser. No. 61/049,465, filed May 1, 2008 and U.S. ProvisionalApplication Ser. No. 61/049,508, filed May 1, 2008, the entire contentsof which are incorporated herein by reference.

FIELD OF THE INVENTION

Generally, the present invention relates to improvements in metalutilization in supported, metal-containing catalysts. For example, thepresent invention relates to methods for directing and/or controllingmetal deposition onto surfaces of porous substrates. More particularly,some embodiments of the present invention relate to methods for treatingporous substrates (e.g., porous carbon substrates or porous metalsubstrates) to provide treated substrates having one or more desirableproperties (e.g., a reduced surface area attributable to pores having anominal diameter within a predefined range) that may be utilized assupports for metal-containing catalysts.

The present invention also relates to methods for preparing catalysts inwhich a first metal is deposited onto a support (e.g., a porous carbonsupport) to provide one or more regions of a first metal at the surfaceof the support, and a second metal is deposited at the surface of theone or more regions of the first metal. Generally, the electropositivityof the first metal (e.g., copper or iron) is greater than theelectropositivity of the second metal (e.g., a noble metal such asplatinum) and the second metal is deposited at the surface of the one ormore regions of the first metal by displacement of the first metal.

The present invention further relates to treated substrates, catalystprecursor structures and catalysts prepared by these methods.

The invention further relates to use of catalysts prepared as detailedherein in catalytic oxidation reactions, such as oxidation of asubstrate selected from the group consisting ofN-(phosphonomethyl)iminodiacetic acid or a salt thereof, formaldehyde,and/or formic acid.

BACKGROUND OF THE INVENTION

N-(phosphonomethyl)glycine (known in the agricultural chemical industryas glyphosate) is described in Franz, U.S. Pat. No. 3,799,758.Glyphosate and its salts are conveniently applied as a post-emergentherbicide in aqueous formulations. It is a highly effective andcommercially important broad-spectrum herbicide useful in killing orcontrolling the growth of a wide variety of plants, includinggerminating seeds, emerging seedlings, maturing and established woodyand herbaceous vegetation, and aquatic plants.

Various methods for producing glyphosate are known in the art, includingvarious methods utilizing carbon-supported noble metal-containingcatalysts. See, for example, U.S. Pat. No. 6,417,133 to Ebner et al. andWan et al. International Publication No. WO 2006/031938. Generally,these methods include the liquid phase oxidative cleavage ofN-(phosphonomethyl) iminodiacetic acid (i.e., PMIDA) in the presence ofa carbon-supported noble metal-containing catalyst. Along withglyphosate product, various by-products may form, such as formaldehyde,formic acid (which is formed by the oxidation of the formaldehydeby-product); aminomethylphosphonic acid (AMPA) and methylaminomethylphosphonic acid (MAMPA), which are formed by the oxidation ofN-(phosphonomethyl)glycine; and iminodiacetic acid (IDA), which isformed by the de-phosphonomethylation of PMIDA. These by-products mayreduce glyphosate yield (e.g., AMPA and/or MAMPA) and may introducetoxicity issues (e.g., formaldehyde). Thus, significant by-productformation is preferably avoided.

It is generally known in the art including, for example, as described inEbner et al. U.S. Pat. No. 6,417,133 and by Wan et al. in InternationalPublication No. WO 2006/031938, that carbon primarily catalyzes theoxidation of PMIDA to glyphosate and the noble metal primarily catalyzesthe oxidation of by-product formaldehyde to carbon dioxide, and water.The catalysts of Ebner et al. U.S. Pat. No. 6,417,133 and Wan et al. WO2006/031938 have proven to be highly advantageous and effectivecatalysts for the oxidation of PMIDA to glyphosate and the oxidation ofby-products formaldehyde and formic acid to carbon dioxide and waterwithout excessive leaching of noble metal from the carbon support. Thesecatalysts are also effective in the operation of a continuous processfor the production of glyphosate by oxidation of PMIDA. Even thoughthese catalysts are effective in PMIDA oxidation and are generallyresistant to noble metal leaching under PMIDA oxidation conditions,there exist opportunities for improvement.

For example, the distribution and/or size of the pores of the poroussubstrates utilized in noble metal-containing catalysts may impactcatalyst performance and metal utilization. Methods to introducecompounds (i.e., pore blocking compounds) within pores of substrates tomodify metal deposition are known in the art. See, for example, U.S.Pat. No. 5,439,859 to Durante et al.

One object of the present invention is development of catalystseffective for the oxidation of PMIDA, formaldehyde, and/or formic acidthat more efficiently utilize the costly noble metal, and methods fortheir preparation. More efficient metal usage may provide catalysts moreactive than conventional catalysts. Another object of the presentinvention is development of methods for preparing effective catalyststhat require a reduced proportion of costly noble metal as compared toconventional catalysts, while still exhibiting suitable activity.

SUMMARY OF THE INVENTION

This invention provides catalysts and methods for preparing catalyststhat are useful in heterogeneous oxidation reactions, including thepreparation of glyphosate by the oxidation of PMIDA.

Briefly, therefore, the present invention is directed to oxidationcatalysts comprising a particulate carbon support, a first metal, and asecond metal, the support having at its surface particles comprising thefirst metal and the second metal.

In at least one embodiment, the second metal distribution within atleast one of the particles as characterized by energy dispersive x-ray(EDX) line scan analysis as described in Protocol B produces a secondmetal signal that varies by no more than about 25% across a scanningregion having a dimension that is at least about 70% of the largestdimension of the at least one particle. In a further embodiment, thesecond metal distribution within at least one of the particles ascharacterized by EDX line scan analysis as described in Protocol Bproduces a second metal signal that varies by no more than about 20%across a scanning region having a dimension that is at least about 60%of the largest dimension of the at least one particle. In anotherembodiment, the second metal distribution within at least one of theparticles as characterized by EDX line scan analysis as described inProtocol B produces a second metal signal that varies by no more thanabout 15% across a scanning region having a dimension that is at leastabout 50% of the largest dimension of the at least one particle.

The present invention is also directed to an oxidation catalystcomprising a particulate carbon support, copper, and platinum, thesupport having at its surface particles comprising copper and platinum.The platinum distribution within at least 70% (number basis) of theparticles as characterized by EDX line scan analysis as described inProtocol B produces a platinum signal that varies by no more than about25% across a scanning region having a dimension that is at least about70% of the largest dimension of said particles.

The present invention is further directed to an oxidation catalystcomprising a particulate carbon support, a first metal, and a noblemetal, the support having at its surface metal particles comprising thefirst metal and the noble metal. The catalyst is characterized aschemisorbing at least 975 μmoles CO per gram of catalyst per gram noblemetal during Cycle 2 of static carbon monoxide chemisorption analysis asdescribed in Protocol A.

The present invention is also directed to an oxidation catalystcomprising a particulate carbon support, a first metal, and a noblemetal, the support having at its surface metal particles comprising thefirst metal and the noble metal, wherein the metal particles comprise acore comprising the first metal and a shell at least partiallysurrounding the core and comprising the noble metal, wherein at leastabout 70% of the noble metal is present within the particle shell.

In a further embodiment, the present invention is directed to anoxidation catalyst comprising a particulate carbon support, platinum,and copper, the support having at its surface metal particles comprisingplatinum and copper, wherein the atom percent of platinum at the surfaceof the particles is at least about 10%.

In a still further embodiment, the present invention is directed to anoxidation catalyst comprising a particulate carbon support, a firstmetal, and a noble metal, the support having at its surface metalparticles comprising the first metal and the noble metal, wherein themetal particles comprise a core comprising the first metal and a shellat least partially surrounding the core and comprising the noble metal;and the catalyst is characterized as chemisorbing at least 975 μmoles COper gram of catalyst per gram noble metal during Cycle 2 of staticcarbon monoxide chemisorption analysis as described in Protocol A.

In another embodiment, the present invention is directed to an oxidationcatalyst comprising a particulate carbon support, platinum, and copper,the support having at its surface metal particles comprising platinumand copper, wherein the atom percent of platinum at the surface of theparticles is at least about 5%; and the catalyst is characterized aschemisorbing at least 500 μmoles CO per gram of catalyst per gram noblemetal during Cycle 2 of static carbon monoxide chemisorption analysis asdescribed in Protocol A.

In a still further embodiment, the present invention is directed to anoxidation catalyst comprising a particulate carbon support, a firstmetal, and a noble metal, the support having at its surface metalparticles comprising the first metal and the noble metal, wherein themetal particles comprise a core comprising the first metal and a shellat least partially surrounding the core and comprising the noble metal;the noble metal constitutes less than 5% by weight of the catalyst; andthe catalyst is characterized as chemisorbing at least about 800 μmolesCO per gram of catalyst per gram noble metal during Cycle 2 of staticcarbon monoxide chemisorption analysis as described in Protocol A.

The present invention is also directed to an oxidation catalystcomprising a particulate carbon support having metal particles at asurface thereof comprising a first metal and a second metal, wherein theelectropositivity of the first metal is greater than theelectropositivity of the second metal and the second metal is depositedby displacement of first metal ions of one or more regions of firstmetal of a catalyst precursor structure; and the weight ratio of thesecond metal to the first metal is at least about 0.25:1.

The present invention is also directed to processes for oxidizing asubstrate selected from the group consisting ofN-(phosphonomethyl)iminodiacetic acid or a salt thereof, formaldehyde,and formic acid. Generally, the process comprises contacting thesubstrate with an oxidizing agent in the presence of an oxidationcatalyst prepared by the methods detailed herein and/or as describedherein. For example, in one embodiment the catalyst comprises a firstmetal, a noble metal, and a porous carbon support, the catalystcomprising one or more first metal regions at the surface of the carbonsupport and one or more noble metal regions at the surface of the one ormore first metal regions, wherein the first metal has anelectropositivity greater than the electropositivity of the noble metal.

The present invention is further directed to various methods forpreparing a catalyst comprising a first metal, a second metal, and aporous support having a surface comprising pores of a nominal diameterwithin a predefined range and pores of a nominal diameter outside thepredefined range.

In one embodiment, the method comprises disposing a pore blocking agentwithin pores of the porous support having a nominal diameter within thepredefined range, the pore blocking agent having at least one dimensionrelative to the openings of the pores having a nominal diameter withinthe predefined range such that the pore blocking agent is preferentiallyretained within the pores; contacting the support with a first metaldeposition bath comprising an aqueous medium and ions of the firstmetal, thereby depositing the first metal at the surface of the poroussupport within the pores having a nominal diameter outside thepredefined range to form a catalyst precursor structure having one ormore regions of the deposited first metal at the surface of the supportamong the pores of a nominal diameter outside the predefined range; andcontacting the catalyst precursor structure with a second metaldeposition bath comprising ions of the second metal, thereby depositingthe second metal at the surface of the catalyst precursor structure.

In another embodiment, the method comprises contacting the support and afirst metal deposition bath comprising an aqueous medium, ions of thefirst metal, and a coordinating agent that forms a coordination compoundwith the first metal having at least one dimension larger than thenominal diameter of the pores within the predefined range, therebydepositing the first metal at the surface of the support within thepores having a nominal diameter outside the predefined range to form acatalyst precursor structure having one or more regions of the depositedfirst metal at the surface of the support; and contacting the catalystprecursor structure with a second metal deposition bath comprising ionsof the second metal, thereby depositing the second metal at the surfaceof the catalyst precursor structure.

The present invention is also directed to methods for preparingcatalysts comprising a first metal, a second metal, and a porous carbonsupport.

In one embodiment, the method comprises contacting the porous carbonsupport with a first metal deposition bath comprising ions of the firstmetal, thereby depositing the first metal at the surface of the porouscarbon support to form a catalyst precursor structure having one or moreregions of the deposited first metal at the surface of the support,wherein the first metal has an electropositivity greater than theelectropositivity of the second metal; contacting the catalyst precursorstructure with a second metal deposition bath comprising ions of thesecond metal, thereby depositing the second metal at the surface of thecatalyst precursor structure by displacement of the first metal from oneor more of the regions; and heating the catalyst precursor structurehaving the first and second metals deposited at the surface of thecatalyst precursor structure to a temperature of at least about 500° C.in a non-oxidizing environment.

In a further embodiment, the method comprises contacting the porouscarbon support with a first metal deposition bath comprising ions of thefirst metal, thereby depositing the first metal at the surface of theporous carbon support to form a catalyst precursor structure having oneor more regions of the deposited first metal at the surface of thesupport, wherein the carbon support has a Langmuir surface area of atleast about 500 m²/g and the first metal has an electropositivitygreater than the electropositivity of the second metal; and contactingthe catalyst precursor structure with a second metal deposition bathcomprising ions of the second metal, thereby depositing the second metalat the surface of the catalyst precursor structure by displacement ofthe first metal from one or more of the regions.

The present invention is also directed to methods for preparing acatalyst comprising a first metal, a noble metal, and a porous support.In one embodiment, the method comprises contacting the support and afirst metal deposition bath comprising an aqueous medium, ions of thefirst metal and a coordinating agent that forms a coordination compoundwith the first metal, thereby depositing the first metal at the surfaceof the support to form a catalyst precursor structure having one or moreregions of the deposited first metal at the surface of the support,wherein the first metal has an electropositivity greater than theelectropositivity of the noble metal; and contacting the catalystprecursor structure with a noble metal deposition bath comprising ionsof the noble metal, thereby depositing the noble metal at the surface ofthe catalyst precursor structure by displacement of the first metal fromone or more of the regions.

In a further embodiment, the method comprises contacting the supportwith a first metal deposition bath comprising an aqueous medium and ionsof the first metal, thereby depositing first metal at the surface of thesupport to form a catalyst precursor structure having one or moreregions of the deposited first metal at the surface of the support,wherein the first metal has an electropositivity greater than theelectropositivity of the noble metal; and contacting the catalystprecursor structure with a noble metal deposition bath comprising ionsof the noble metal, thereby depositing the noble metal at the surface ofthe catalyst precursor structure by displacement of the first metal fromone or more of the regions, wherein substantially all the noble metal isdeposited by the displacement, or the noble metal ions consistessentially of noble metal ions having an oxidation number of 2.

In another embodiment, the method comprises contacting the support witha first metal deposition bath comprising an aqueous medium, ions of thefirst metal, and a pore blocking agent, thereby disposing the poreblocking agent within pores of the substrate having a nominal diameterwithin a predefined range, wherein the pore blocking agent has at leastone dimension relative to the opening of the pores of the predefinedrange sufficient such that the pore blocking agent is preferentiallyretained within the pores, and depositing first metal at the surface ofthe support within pores having a nominal diameter outside thepredefined range, thereby forming a catalyst precursor structure havingone or more regions of the deposited first metal at the surface of thesupport, wherein the first metal has an electropositivity greater thanthe electropositivity of the noble metal; and contacting the catalystprecursor structure with a noble metal deposition bath comprising ionsof the noble metal, thereby depositing the noble metal at the surface ofthe catalyst precursor structure by displacement of the first metal fromone or more of regions.

The present invention is also directed to methods for preparing acatalyst comprising a first metal, a noble metal, and a porous supporthaving a surface comprising pores of a nominal diameter within apredefined range and pores of a nominal diameter outside the predefinedrange. In one embodiment, the method comprises contacting the supportand a first metal deposition bath comprising an aqueous medium, ions ofthe first metal and a coordinating agent that forms a coordinationcompound with the first metal having at least one dimension larger thanthe nominal diameter of the pores within the predefined range, therebydepositing the first metal at the surface of the support within thepores having a nominal diameter outside the predefined range to form acatalyst precursor structure having one or more regions of the depositedfirst metal at the surface of the support; and contacting the catalystprecursor structure with a noble metal deposition bath comprising ionsof the noble metal, thereby depositing the noble metal at the surface ofthe catalyst precursor structure.

The present invention is also directed to methods for preparingcatalysts comprising copper, platinum, and a porous carbon support.

In one embodiment, the method comprises contacting the support with acopper deposition bath comprising copper ions and a coordinating agentin the absence of an externally applied voltage, thereby depositingcopper at the surface of the porous carbon support to form a catalystprecursor structure having one or more regions of deposited copper atthe surface of the support; and contacting the catalyst precursorstructure and a platinum deposition bath comprising platinum ions,thereby depositing platinum at the surface of the catalyst precursorstructure by displacement of copper from one or more of the regions.

In another embodiment, the method comprises contacting the support and acopper deposition bath comprising copper ions in the absence of anexternally applied voltage, thereby depositing copper at the surface ofthe carbon support to form a catalyst precursor structure having one ormore regions of deposited copper at the surface of the support, whereinthe carbon support has a Langmuir surface area of at least about 500m²/g prior to deposition of copper thereon; and contacting the catalystprecursor structure and a platinum deposition bath comprising platinumions, thereby depositing platinum at the surface of the catalystprecursor structure by displacement of copper from one or more of theregions.

In a further embodiment, the method comprises contacting the support anda copper deposition bath comprising copper ions in the absence of anexternally applied voltage, thereby depositing copper at the surface ofthe carbon support to form a catalyst precursor structure having one ormore regions of deposited copper at the surface of the support;contacting the catalyst precursor structure and a platinum depositionbath comprising platinum ions, thereby depositing platinum at thesurface of the catalyst precursor structure by displacement of copperfrom one or more of the regions; and heating the surface of the catalystprecursor having platinum at the surface of the one or more copperregions to a temperature of at least about 500° C. in a non-oxidizingenvironment.

The present invention is also directed to methods for preparingcatalysts comprising iron, platinum, and a porous carbon support.

In one embodiment, the method comprises contacting the support with aniron deposition bath comprising iron ions and a coordinating agent inthe absence of an externally applied voltage, thereby depositing iron atthe surface of the porous carbon support to form a catalyst precursorstructure having one or more regions of deposited iron at the surface ofthe support; and contacting the catalyst precursor structure and aplatinum deposition bath comprising platinum ions, thereby depositingplatinum at the surface of the catalyst precursor structure bydisplacement of iron from one or more of the regions.

In another embodiment, the method comprises contacting the support andan iron deposition bath comprising iron ions in the absence of anexternally applied voltage, thereby depositing iron at the surface ofthe carbon support to form a catalyst precursor structure having one ormore regions of deposited iron at the surface of the support, whereinthe carbon support has a Langmuir surface area of at least about 500m²/g prior to deposition of iron thereon; and contacting the catalystprecursor structure and a platinum deposition bath comprising platinumions, thereby depositing platinum at the surface of the catalystprecursor structure by displacement of iron from one or more of theregions.

In a further embodiment, the method comprises contacting the support andan iron deposition bath comprising iron ions in the absence of anexternally applied voltage, thereby depositing iron at the surface ofthe carbon support to form a catalyst precursor structure having one ormore regions of deposited iron at the surface of the support; contactingthe catalyst precursor structure and a platinum deposition bathcomprising platinum ions, thereby depositing platinum at the surface ofthe catalyst precursor structure by displacement of iron from one ormore of the regions; and heating the surface of the catalyst precursorhaving platinum at the surface of the one or more iron regions in anon-oxidizing environment.

The present invention is also directed to methods for treating a poroussubstrate to prepare a modified porous substrate having a reducedsurface area attributable to pores having a nominal diameter within apredefined range.

In one embodiment, the method comprises disposing a pore blocking agentwithin pores of the porous substrate having a nominal diameter withinthe predefined range, the pore blocking agent having at least onedimension relative to the opening of the pores having a nominal diameterwithin the predefined range sufficient such that the pore blocking agentis preferentially retained within the pores.

In another embodiment, the method comprises introducing a pore blockingcompound into the pores of the porous substrate, the pore blockingcompound being susceptible to a conformational change such that the poreblocking compound is retained within pores of the porous substratehaving a diameter within the predefined range.

In a further embodiment, the method comprises introducing into the poreshaving a nominal diameter within a predefined range compounds capable offorming a pore blocking compound having at least one dimension such thatthe pore blocking compound is retained within the pores having a nominaldiameter within a predefined range.

The present invention is also directed to methods for treating poroussubstrates having micropores and larger diameter pores to prepare amodified porous substrate having a reduced micropore surface area.

In one embodiment, the method comprises disposing a pore blocking agentwithin micropores of the porous substrate, the pore blocking agenthaving at least one dimension relative to the micropore openings suchthat the pore blocking agent is preferentially retained within thepores.

In another embodiment, the method comprises introducing a pore blockingcompound into the micropores of the porous substrate, the pore blockingcompound being susceptible to a conformational change such that the poreblocking compound is retained within micropores of the porous substrate.

In a further embodiment, the method comprises introducing into themicropores of the substrate compounds capable of forming a pore blockingcompound having at least one dimension such that the pore blockingcompound is retained within the micropores.

In a still further embodiment, the method comprises introducing a poreblocking composition into the micropores of the porous substrate, thepore blocking composition comprising a substituted cyclohexanederivative.

The present invention is also directed to methods for preparing acatalyst comprising a metal at the surface of a porous substrate whereinthe metal is preferentially excluded from pores of the porous substratehaving a nominal diameter within a predefined range. In one embodiment,the method comprises (i) introducing one or more precursors of a poreblocking compound into pores of the porous substrate, wherein: at leastone of the pore blocking compound precursors is susceptible to aconformational change to form a pore blocking compound that is retainedwithin pores of the porous substrate having a nominal diameter withinthe predefined range, or at least two pore blocking compound precursorsare capable of forming a pore blocking compound having at least onedimension such that the pore blocking compound is retained within poresof the porous substrate having a nominal diameter within a predefinedrange; (ii) preferentially removing the pore blocking compound from thepores of the porous substrate having a nominal diameter outside thepredefined range to prepare a modified porous substrate having a reducedsurface area attributable to pores having a nominal diameter within thepredefined range; and (iii) contacting the surface of the modifiedporous substrate with a solution containing the metal.

In another embodiment, the present invention is directed to a poroussubstrate having a pore blocking compound within pores of the poroussubstrate having a nominal diameter within a predefined range. The poreblocking compound is retained within the pores having a nominal diameterwithin a predefined range due to the pore blocking compound having atleast one dimension that is greater than openings of the pores having anominal diameter within a predefined range, or the pore blockingcompound exhibiting a conformation that prevents the pore blockingcompound from exiting through openings of pores having a nominaldiameter within the predefined range.

The present invention is directed to treated porous substrates having apore blocking compound within micropores of the porous substrate. In oneembodiment, the micropore surface area of the treated substrate is nomore than about 70% of the micropore surface area of the poroussubstrate prior to treatment. In another embodiment, the pore blockingcompound is selected from the group consisting of the condensationproduct of a substituted cyclohexane derivative and a glycol, thecondensation product of a di-substituted cyclohexane derivative and aglycol, and combinations thereof.

Other objects and features will be in part apparent and in part pointedout hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C are graphical representations of pore blockers in accordancewith the present invention.

FIG. 1D illustrates a conformational change of a pore blocker inaccordance with the present invention.

FIG. 2 depicts heat treatment of a first and second metal-impregnatedsupport in accordance with the present invention.

FIGS. 3A/5A and 3B/5B transmission electron microscopy (TEM) results asdescribed in Example 3.

FIGS. 4A and 4B provide pore volume and surface area for treated anduntreated substrates as described in Example 4.

FIG. 5C provides porosity data for catalysts analyzed as described inExample 19.

FIG. 5D provides pore volume results for catalysts analyzed as describedin Example 20.

FIGS. 6-13 are micrographs generated by scanning transmission electronmicroscopy (STEM) analysis for a carbon support and metal-impregnatedsupports as described in Example 21.

FIG. 14 provides results of line scan analysis for a metal-impregnatedsupport as described in Example 21.

FIGS. 15 and 16 are STEM micrographs for catalysts as described inExample 21.

FIGS. 17 and 18 are results of energy dispersive spectroscopy (EDS)analysis of catalysts as described in Example 21.

FIGS. 19-21 are STEM micrographs for reaction-tested catalysts asdescribed in Example 21.

FIG. 22 provides results of line scan analysis for a reaction-testedcatalyst as described in Example 21.

FIGS. 23 and 24 are STEM micrographs for reaction-tested catalysts asdescribed in Example 21.

FIG. 25 provides results of line scan analysis for a reaction testedcatalyst as described in Example 21.

FIGS. 26 and 27 are EDS spectra for reaction-tested catalysts asdescribed in Example 21.

FIGS. 28 and 29 are TEM and STEM images for metal-impregnated supportsas described in Example 22.

FIGS. 30-31, 32-33, 34-35, and 36-37 are TEM images and correspondingline scan analysis results for metal-impregnated supports as describedin Example 22.

FIGS. 38 and 39 are TEM and STEM images for catalysts as described inExample 22.

FIG. 40 indicates the portion of catalyst analyzed by line scan analysisas described in Example 22.

FIG. 41 provides line scan analysis for the portion of the supportidentified in FIG. 40.

FIG. 42 indicates the portion of catalyst analyzed by line scan analysisas described in Example 22.

FIG. 43 provides line scan analysis for the portion of the supportidentified in FIG. 40.

FIGS. 44 and 45 are TEM images utilized in particle size analysis asdescribed in Example 23.

FIG. 46 provides particle size distribution data for catalyst analyzedas described in Example 23.

FIGS. 47 and 48 are TEM images utilized in particle size analysis asdescribed in Example 23.

FIG. 49 provides particle size distribution data for catalyst analyzedas described in Example 23.

FIGS. 50 and 51 are X-ray diffraction results for a catalyst analyzed asdescribed in Example 24.

FIGS. 52-55 are nano-diffraction results for a metal particle analyzedas described in Example 24.

FIGS. 56 and 57 provide reaction testing data as described in Example25.

FIG. 58 provides reaction testing data of Example 26.

FIGS. 59-62 provide reaction testing data of Example 27.

FIGS. 63-65 provide reaction testing data of Example 28.

FIGS. 66-68 provide reaction testing data of Example 29.

FIGS. 69-71 provide reaction testing data of Example 30.

FIGS. 72-78 provide reaction testing data of Example 31.

FIGS. 79-84 provide reaction testing data of Example 32.

FIG. 85 provides reaction testing data of Example 33.

FIGS. 86-90 provide reaction testing data of Example 34.

FIGS. 91-95 provide reaction testing data of Example 35.

FIGS. 96-98 provide reaction testing data of Example 36.

FIG. 99 provides reaction testing data of Example 37.

FIG. 100 provides reaction testing data of Example 38.

FIGS. 101 and 102 provide reaction testing data of Example 39.

FIG. 103 provides platinum site density data as described in Example 20.

FIG. 104 provides reaction testing data of Example 41.

FIGS. 105 and 106 provide reaction testing data of Example 42.

FIG. 107 provides reaction testing data of Example 43.

FIG. 108 provides reaction testing data of Example 44.

FIG. 109 provides X-Ray Diffraction (XRD) results for the catalystdescribed in Example 45.

FIGS. 110 and 111 provide XRD results for the catalyst described inExample 46.

FIG. 111A provides platinum leaching data for catalysts described inExamples 46 and 48.

FIGS. 112-115 provide XRD results for the catalysts described in Example50.

FIG. 116 is a scanning transmission electron microscopy (STEM)micrograph described in Example 55.

FIGS. 117 and 118 are energy dispersive x-ray (EDX) spectroscopy linescan results described in Example 55.

FIGS. 119 and 120 are STEM photomicrographs described in Example 55.

FIG. 121 is an STEM micrograph described in Example 55.

FIG. 122 provides electron energy loss spectroscopy (EELS) line scanresults described in Example 55.

FIG. 123 is an STEM micrograph described in Example 55.

FIG. 124 provides EELS line scan results described in Example 55.

FIG. 125 is an STEM micrograph described in Example 55.

FIG. 126 provides EELS line scan results described in Example 55.

FIG. 127 provides high resolution electron microscopy (HREM)photomicrographs described in Example 57.

FIG. 128 provides STEM micrographs described in Example 57.

FIG. 129 is an STEM micrograph described in Example 57.

FIG. 130 provides EDX line scan analysis results described in Example57.

FIG. 131 is an STEM micrograph described in Example 57.

FIG. 132 provides EDX line scan analysis results described in Example57.

FIG. 133 is an STEM photomicrograph described in Example 57.

FIG. 134 provides results of EELS line scan analysis described inExample 57.

FIGS. 135-137 are HREM photomicrographs described in Example 57.

FIG. 138 provides XRD results described in Example 57.

FIG. 139 is an STEM micrograph described in Example 60.

FIG. 140 provides results of EELS line scan analysis described inExample 60.

FIG. 141 is an STEM micrograph described in Example 60.

FIG. 142 provides EDX line scan analysis results described in Example60.

FIG. 143 is an STEM micrograph described in Example 60.

FIG. 144 provides results of EELS line scan analysis described inExample 60.

FIG. 145 provides EDX line scan analysis results described in Example60.

FIG. 146 is an STEM micrograph described in Example 60.

FIG. 147 provides EDX line scan analysis results described in Example60.

FIG. 148 provides XRD results described in Example 60.

FIGS. 149 and 150 are STEM micrographs described in Example 60.

FIG. 151 provides EDX line scan analysis results described in Example60.

FIG. 152 is an STEM micrograph described in Example 60.

FIG. 153 provides EDX line scan analysis described in Example 60.

FIGS. 154 and 155 provide XRD results described in Example 61.

FIGS. 155A and 155B provide microscopy results for a finished catalystas described in Example 65.

FIGS. 155C-155F provide microscopy results for a finished catalystdescribed in Example 65.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Described herein are catalyst preparation methods providing improvementsin metal utilization in supported, metal-containing catalysts.Generally, various embodiments of the present invention includecontrolling and/or directing metal deposition onto the surface of aporous substrate. Controlling or directing metal deposition can be usedto address one or more problems associated with the preparation ofconventional supported, metal-containing catalysts.

For example, one potential drawback associated with conventionalplatinum on carbon catalysts is the susceptibility of relatively smallplatinum-containing particles to leaching during liquid phase catalyticoxidation reactions as compared to larger metal-containing particles.Excessive leaching of metal particles results in metal loss andrepresents inefficient metal usage. Furthermore, in the case of PMIDAoxidation, these relatively small platinum-containing crystallites arebelieved to contribute to undesired by-product formation (e.g., IDA).Relatively small platinum-containing crystallites are also believed tobe more susceptible to deactivation than larger particles (e.g., bydeactivation of metal-containing active sites in the presence of thereaction medium and/or by coking of the catalyst). It is believed that asignificant portion of the relatively small metal particles are at thesurface of the carbon support within relatively small pores and that thesmall pores may act to trap and prevent these relatively small platinumcrystallites from agglomerating into larger particles that are generallymore resistant to leaching and generally do not promote IDA formation.In addition, metal deposited at the surface of a porous substrate withinthe relatively small pores is believed to be less accessible toreactants than metal deposited within larger pores, and therebycontributes less to catalyst activity.

Various methods described herein for directing and/or controlling metaldeposition generally involve treating porous substrates by disposing orintroducing one or more pore blocking compounds within pores of apredefined size range. The methods described herein may be used toselectively block pores within a certain size domain withoutsignificantly affecting other pores of the substrate so as to provideadvantageous catalytic surface area. As detailed herein, including theExamples, various embodiments of the present invention provide a poroussubstrate including a pore blocking compound disposed and preferentiallyretained within relatively small pores (e.g., micropores, or poreshaving a nominal diameter of less than about 20 Å). The presence of thepore blocking compound within the pores of the substrate may beindicated by a reduced proportion of surface area attributable to therelatively small pores (e.g., a reduced proportion of micropore surfacearea) and/or by a reduced contribution to the porosity of the substrateby the relatively small pores. It is believed that the presence of thepore blocking compound within the micropores of the treated substratereduces, and preferably substantially prevents, metal deposition at thesubstrate surfaces within these pores, thereby directing metaldeposition to other surfaces of the substrate and within larger pores.The presence of the pore blocker is thus currently believed to reduceformation of small metal crystallites within the micropores that areresistant to agglomeration, readily leached and/or deactivated, andrepresent inefficient metal usage.

In addition to or separate from the effect of controlling or directingthe location of metal deposition (e.g., by disposing within orintroducing a pore blocking compound into pores of a substrate), themanner of metal deposition may promote more efficient metal usage aswell. For example, various catalysts described herein include and/or areprepared from a support having one or more regions of a first metal atthe surface of the support, and a second metal at the surface of the oneor more regions of the first metal.

The first metal is selected to have a greater electropositivity than thesecond metal and the second metal is deposited at the surface of the oneor more regions of the first metal by displacement of the first metalfrom the one or more regions at the surface of the support. Moreparticularly, the second metal may be deposited by near atom-for-atomreplacement of the first metal by the second metal. It is currentlybelieved that metal deposition in this manner promotes formation of arelatively thin layer comprising second metal atoms and may in fact forma near monolayer of second metal atoms deposited at the surface of thefirst metal regions (e.g., a layer of second metal atoms at the surfaceof the one or more regions of first metal no more than about 3 atomsthick). Heating the carbon support having the first and second metalsthereon forms metal particles comprising the first and second metal. Themetal particles formed contain the second metal in a form thatrepresents more efficient second metal utilization. For example, thecomposition of a significant fraction of the metal particles isgenerally rich in first metal content, thereby providing a relativelylow proportion of unexposed second metal throughout the particles (e.g.,a first metal-rich bimetallic alloy). Additionally or alternatively,metal particles formed upon subsequent heating may have a relativelythin shell comprising the second metal (e.g., a layer no more than about3 atoms thick) at least partially surrounding a core predominantlycomprising the first metal.

I. Porous Substrate Treatment

Disposing within and/or introducing a pore blocking agent or compound(also referred to herein as a pore blocker) into pores of a poroussubstrate generally comprises contacting the substrate with the agent orcompound, or a precursor (or precursors) thereof. In one embodiment, thepore blocking compound is preferentially retained within pores of thesubstrate within a selected size domain (e.g., micropores) by virtue ofhaving at least one dimension larger than the openings of the pores,thereby inhibiting the agent from exiting the selected pores. In variousembodiments, the pore blocking agent may be formed from one or more poreblocking agent precursors introduced into the substrate pores.Additionally or alternatively, and regardless of whether the poreblocking agent is introduced into the pores or formed in situ (i.e.,formed from one or more agent precursors introduced into the pores), theagent may be retained within pores of the substrate within a selectedsize domain by virtue of an induced conformational change in the poreblocking agent such that the pore blocking agent is dimensionallyinhibited from exiting the selected pores. A conformational change inthe pore blocking agent may be induced within selected pores by virtueof interactions between the pore blocking agent and the walls of thepores. In accordance with one embodiment, a pore blocking agent isdisposed within and preferentially retained within micropores of theporous substrate to produce a treated substrate for metal depositionexhibiting a reduced proportion of micropore surface area.

It is to be understood that reference to one or more precursorscontemplates compositions that ultimately function as a pore blockingagent upon entry into pores (e.g., by virtue of at least one dimensionof the compound and/or by virtue of a conformational change in thecompound after entry into the pores). Additionally or alternatively,reference to one or more precursors may refer to one or more compoundsthat combine or react to form the pore blocking agent once disposedwithin and/or introduced into the pores of the substrate. Regardless ofwhether a compound that ultimately functions as the pore blocker isintroduced into or disposed within the pores of the substrate, orwhether components that combine to form the pore blocker are introducedinto or disposed within the pores, the mechanism by which the poreblocker is believed to function (i.e., by virtue of having at least onedimension larger than pore openings, either initially or following aconformational change) is the same.

In various embodiments the pore blocker comprises a compound having atleast one dimension such that, after entry into pores, the pore blockeris preferentially retained within those pores falling within a selectedsize domain. Of course, it is to be understood that the pore blockerlikewise typically has at least one dimension that permits entry intothe pores, but it is currently believed that the pore blocker typicallyassumes an orientation and/or conformation within the pores such thatthe dimension greater than the pore opening prevents the pore blockingcompound from exiting the pore.

As noted above, in accordance with one embodiment, the pore blocker ispreferentially retained within substrate micropores. However, this doesnot exclude the pore blocker or precursor(s) thereof from also enteringpores of a size that are not within this predefined range upon contactwith the porous substrate. For example, pore blocker may enter poreshaving a nominal diameter greater than about 20 Å (e.g., pores having anominal diameter of from about 20 Å to about 3000 Å, commonly referredas meso- and macropores), but the pore blocker tends to subsequentlyexit and not be preferentially retained within these pores, although thepore blocking agent may remain in a minor portion of pores outside themicropore range.

A. Porous Substrate

Generally, the porous substrate or supporting structure for thecatalytic metal-containing active phase may comprise any materialsuitable for deposition of one or more metals thereon. Preferably, theporous substrate is in the form of a carbon support. In general, thecarbon supports used in the present invention are well known in the artincluding, for example, those detailed in U.S. Pat. No. 6,417,133 toEbner et al. and by Wan et al. in WO 2006/031938 (the entire contents ofwhich are incorporated herein by reference for all relevant purposes).Activated, non-graphitized carbon supports are preferred for noble metalon carbon catalysts used for PMIDA oxidation and provide the catalystwith robust mechanical integrity and high surface area for themetal-containing active phase. However, activated, non-graphitizedcarbon supports are not necessarily preferred in all instances and itshould be understood that suitable catalysts for various otherapplications may be prepared utilizing carbon supports that are notactivated and/or non-graphitized. In various particularly preferredembodiments, the supports are in the form of particulates (e.g.,powders).

In various preferred embodiments (e.g., catalysts used for PMIDAoxidation), the carbon support contains a relatively low proportion ofoxygen-containing functional groups (e.g., carboxylic acids, ethers,alcohols, aldehydes, lactones, ketones, esters, amine oxides, andamides). These functional groups may increase noble metal leaching andpotentially increase noble metal agglomeration and particle growthduring liquid phase oxidation reactions and thus reduce the ability ofthe catalyst to oxidize oxidizable substrates (e.g., PMIDA and/orformaldehyde). As used herein, an oxygen-containing functional group is“at the surface of the carbon support” if it is bound to an atom of thecarbon support and is able to chemically or physically interact withcompositions within the reaction mixture or with the metal atomsdeposited on the carbon support. As described in U.S. Pat. No. 6,417,133and by Wan et al. in WO 2006/031938, many of the oxygen-containingfunctional groups that reduce noble metal resistance to leaching andsintering and reduce the activity of the catalyst desorb from the carbonsupport as carbon monoxide when the catalyst is heated at a hightemperature (e.g., 900

C) in an inert atmosphere (e.g., helium or argon). Thus, measuring theamount of CO desorption from a fresh catalyst (i.e., a catalyst that hasnot previously been used in a liquid phase oxidation reaction) underhigh temperatures is one method that may be used to analyze the surfaceof the catalyst to predict noble metal retention and maintenance ofcatalyst activity. One way to measure CO desorption is by usingthermogravimetric analysis with in-line mass spectroscopy (“TGA-MS”).Preferably, no more than about 1.2 mmole of carbon monoxide per gram ofcatalyst desorb from the catalyst of the present invention when a dry,fresh sample of the catalyst, after being heated at a temperature ofabout 500° C. for about 1 hour in a hydrogen atmosphere and before beingexposed to an oxidant following the heating in the hydrogen atmosphere,is heated in a helium atmosphere is subjected to a temperature which isincreased from about 20° C. to about 900

C at about 10

C per minute, and then held constant at about 900

C for about 30 minutes. More preferably, no more than about 0.7 mmole ofcarbon monoxide per gram of fresh catalyst desorb under thoseconditions, even more preferably no more than about 0.5 mmole of carbonmonoxide per gram of fresh catalyst desorb, and most preferably no morethan about 0.3 mmole of carbon monoxide per gram of fresh catalystdesorb. A catalyst is considered “dry” when the catalyst has a moisturecontent of less than about 1% by weight. Typically, a catalyst may bedried by placing it into a N₂ purged vacuum of about 25 inches of Hg anda temperature of about 120

C for about 16 hours.

As further described in U.S. Pat. No. 6,417,133 and by Wan et al. in WO2006/031938, measuring the number of oxygen atoms at the surface of afresh catalyst support is another method to analyze the catalyst topredict noble metal retention and maintenance of catalytic activity.Using, for example, x-ray photoelectron spectroscopy, a surface layer ofthe support which is about 50 Å in thickness is analyzed. Preferably,this analysis for a support suitable for use in connection with theoxidation catalysts described herein indicates a ratio of carbon atomsto oxygen atoms at the surface of the support of at least about 20:1.More preferably, the ratio is at least about 30:1, even more preferablyat least about 40:1, even more preferably at least about 50:1, and mostpreferably at least about 60:1. In addition, the ratio of oxygen atomsto metal atoms at the surface preferably is less than about 8:1. Morepreferably, the ratio is less than about 7:1, even more preferably lessthan about 6:1, and most preferably less than about 5:1.

Typically, a support that is in particulate form may comprise a broadsize distribution of particles. For powders, preferably at least about95% of the particles are from about 2 to about 300 μm in their largestdimension, more preferably at least about 98% of the particles are fromabout 2 to about 200 μm in their largest dimension, and most preferablyabout 99% of the particles are from about 2 to about 150 μm in theirlargest dimension with about 95% of the particles being from about 3 toabout 100 μm in their largest dimension. Particles greater than about200 μm in their largest dimension tend to fracture into super-fineparticles (i.e., less than 2 μm in their largest dimension), which maybe more difficult to recover.

In the following discussion, specific surface areas of carbon supportsand catalysts are typically provided in terms of the well-known Langmuirmethod using N₂. It is to be understood that these values generallycorrespond to those measured by the likewise well-knownBrunauer-Emmett-Teller (B.E.T.) method using N₂.

The specific surface area of the carbon support prior to any treatment(e.g., disposing or introducing a pore blocking compound within pores ofa substrate) in accordance with the present invention is generally atleast about 500 m²/g, at least about 750 m²/g, at least about 1000 m²/g,or at least about 1250 m²/g. Typically, the specific surface area of thecarbon support is from about 10 to about 3000 m²/g, more typically fromabout 500 to about 2100 m²/g, and still more typically from about 750 toabout 1900 m²/g or from about 1000 to about 1900 m²/g. In certainembodiments, the preferred specific surface area is from about 1000 toabout 1700 m²/g, 1000 to about 1500 m²/g, from about 1100 to about 1500m²/g, from about 1250 to about 1500 m²/g, from about 1200 to about 1400m²/g, or about 1400 m²/g. Further in accordance with the presentinvention, the porous carbon support generally has a pore volume of atleast about 0.1 ml/g, at least about 0.2 ml/g, or at least about 0.4ml/g. Typically, the porous carbon support has a pore volume of fromabout 0.1 to about 2.5 ml/g, more typically from about 0.2 to about 2.0ml/g and, still more typically, of from about 0.4 to about 1.5 ml/g.

It is to be noted that the present discussion focuses on pore blockingtreatment to reduce micropore surface area of porous carbon substratesor supports for use in noble metal-containing catalysts suitable for usein PMIDA oxidation. However, it is to be understood that methods fortreating a porous substrate by introduction of a pore blocking compoundas described herein are generally applicable to preferentially blockingother pore size domains, other types of porous catalyst supports and/orporous carbon substrates used as supports for metals other than noblemetals. For example, the methods of the present invention are suitablefor treatment of porous Raney metals or alloys often referred to assponges, such as those described in U.S. Pat. No. 7,329,778 toMorgenstern et al. and used as supports for copper-containing catalystsused in the dehydrogenation of primary amino alcohols. By way of furtherexample, the methods of the present invention are also suitable fortreatment of other non-carbon porous supports such as, for example,silicon dioxide (SiO₂), aluminum oxide (Al₂O₃), zirconium oxide (ZrO₃),titanium oxide (TiO₂), and combinations thereof.

B. Pore Blocking

In accordance with the present invention, the pore blocker used toselectively block micropores may be selected from a variety of compoundsincluding, for example, various sugars (e.g., sucrose), 5- or 6-memberring-containing compounds (e.g., 1,3- and 1,4-disubstitutedcyclohexanes), and combinations thereof. Compounds suitable for use inconnection with selective blocking of micropores include1,4-cyclohexanedimethanol (1,4-CHDM), 1,4-cyclohexanedione bis(ethyleneketal), 1,3- or 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexane dionemonoethylene acetal, and combinations thereof.

In various embodiments, the pore blocker may comprise the product of areaction (e.g., a condensation reaction) between one or more poreblocking compound precursors. Once formed, the resulting pore blockingcompound may be preferentially retained within selected pores of thesubstrate by virtue of having at least one dimension that prevents thepore blocking compound from exiting the pores.

For example, it has been observed that the coupling product of acyclohexane derivative and a glycol may be utilized as a micropore poreblocking agent for particulate carbon substrates used to support a noblemetal or other metal catalyst. More particularly, the pore blockingagent may be the coupling product of a di-substituted, tri-substituted,or tetra-substituted cyclohexane derivative and a glycol. In particular,the cyclohexane derivative may be selected from the group consisting of1,4-cyclohexanedione, 1,3-cyclohexanedione,1,4-cyclohexanebis(methylamine), and combinations thereof. The glycol isgenerally selected from the group consisting of ethylene glycol,propylene glycol, and combinations thereof.

Generally, the substrate is contacted with a liquid comprising the poreblocking agent or one or more precursor(s) of the pore blocking agent.Typically, the substrate to be treated is contacted with a mixture orsolution comprising one or more pore blocking compounds or precursor(s)dispersed or dissolved in a liquid contacting medium (e.g., deionizedwater). For example, the substrate may be contacted with a mixture orsolution including a cyclohexane derivative and a glycol, or a liquidcontacting medium consisting essentially of the cyclohexane derivativeand glycol. The substrate may also be sequentially contacted withliquids or liquid media comprising one or more of the precursors. Thecomposition of the liquid including the pore blocking agent or aprecursor(s) thereof contacted with the porous substrate is not narrowlycritical and may be readily selected and/or optimized by one skilled inthe art.

As noted, regardless of whether a compound that ultimately functions asa pore blocker is introduced into pores of the substrate or precursorsthat form the blocking compound are introduced into the substrate, poreblockers may be preferentially retained within selected substrate pores(e.g., micropores) by virtue of the conformational arrangement assumedby the pore blocking agent once disposed or formed within the pores. Forexample, it is currently believed that various pore blocker moleculestransform from a more linear chair conformation to a bulkier boatconformation, which conduces trapping of the compound within themicropores. In particular, it is currently believed that various poreblocking agents including a hydrophilic end group will favor a boatconformation within the micropore(s) of a porous carbon support becauseof the nature of the carbon support (i.e., the boat conformation will befavored by a pore blocking compound having hydrophilic end groupsbecause of the relatively hydrophobic nature of the carbon supportsurface). Examples of pore blocking compounds including a hydrophilicend group include 1,4-cyclohexanedicarboxylic acid and1,4-cyclohexanedimethanol (CHDM).

A conformational change of a pore blocker also may be promoted orinduced by manipulating the liquid medium comprising the pore blockingagent in contact with the substrate including, for example, adjustingthe pH and/or adjusting the temperature of the liquid medium.

FIGS. 1A-1C provide graphical representations of pre-formed poreblockers and pore blocker molecules formed from precursors within thepore (i.e., in situ coupling) that undergo a conformational changewithin the pore to selectively block or plug smaller pores.Conformational change of a cyclohexane pore blocker is shown generallyin FIG. 1D. These depictions are for illustrative purposes and are notintended to limit the present invention.

As noted, it is believed that contacting the substrate with the poreblocking agent or precursors results in pore blocking agent beingintroduced into or disposed within substrate micropores, and withinlarger pores outside this predefined range. In order to provide atreated substrate in which the micropores within the predefined rangeare preferentially blocked, the substrate is subsequently contacted witha washing liquid to remove the blocking agent from pores outside themicropore domain (i.e., those pores in which the pore blocking agentwill not be preferentially retained by virtue of the agent having atleast one dimension larger than the pore opening). The precisecomposition of the washing liquid and manner of its contact with thesubstrate are not narrowly critical, but the substrate may suitably becontacted with deionized water for this purpose.

C. Treated Substrates

As noted, the substrate treatment method of the present invention issuitable for introducing a pore blocking agent into the micropores ofporous substrates (e.g., a particulate carbon support) andpreferentially retaining the pore blocking agent in the micropores.Preferential retention of the pore blocking agent within micropores maybe represented by the proportion of micropores in which the agent isretained. Typically, the pore blocking compound remains in at leastabout 2%, at least about 5%, at least about 10%, or at least about 20%of the micropores, basis the total number of substrate micropores.

Preferential retention of the pore blocking compound within microporesmay also be indicated by the treated substrate surface area provided bymicropores and provided by larger pores. It is believed that thepresence of the pore blocking compound within micropores will cause atleast a portion of these “blocked” pores to appear as a non-porousportion of the treated substrate during surface area measurement methods(e.g., the well-known Langmuir surface area measuring method), therebyreducing the proportion of surface area that would otherwise beattributable to the micropores if they were not blocked. Thispreferential blocking of the targeted pores results in a reduction inthe surface area provided by the micropores (i.e., micropore surfacearea). For example, in various embodiments, the micropore surface areaof the treated substrate is generally no more than about 70%, no morethan about 60%, or no more than about 50% of the micropore surface areaof the substrate prior to treatment by contact with the pore blocker.Preferably, the micropore surface area of the treated substrate is nomore than about 40%, more preferably no more than about 30% and, stillmore preferably, no more than about 20% of the micropore surface area ofthe substrate prior to treatment.

D. Methods for Preparing Catalysts Using Treated Substrates

As detailed herein, catalysts may be prepared by a process generallycomprising depositing one or more noble metals and optionally one ormore promoter metals at the surface of a treated (i.e., pore blocked)substrate such as a porous carbon support and heating the carbon supporthaving the noble metal and optional promoter(s) deposited thereon in anon-oxidizing environment.

The noble metal is generally selected from the group consisting ofplatinum, palladium, ruthenium, rhodium, iridium, silver, osmium, gold,and combinations thereof. In various preferred embodiments, the noblemetal comprises platinum and/or palladium. In still further preferredembodiments, the noble metal is platinum. One or more promoter metals isgenerally selected from the group consisting of tin, cadmium, magnesium,manganese, nickel, aluminum, cobalt, bismuth, lead, titanium, antimony,selenium, iron, rhenium, zinc, cerium, zirconium, tellurium, germanium,and combinations thereof at a surface of the porous substrate and/or asurface of the noble metal.

The noble metal may be deposited in accordance with conventional methodsknown in the art including, for example, liquid phase deposition methodssuch as reactive deposition techniques (e.g., deposition via reductionof noble metal compounds and deposition via hydrolysis of noble metalcompounds), ion exchange techniques, excess solution impregnation, andincipient wetness impregnation; vapor phase methods such as physicaldeposition and chemical deposition; precipitation; electrochemicaldeposition; and electroless deposition as described in U.S. Pat. No.6,417,133 and by Wan et al. in International Publication No. WO2006/031938. In various preferred embodiments, the noble metal isdeposited via a reactive deposition technique comprising contacting thecarbon support with a solution comprising a salt of the noble metal, andthen hydrolyzing the salt. An example of a relatively inexpensivesuitable platinum salt is hexachloroplatinic acid (H₂PtCl₆).

A promoter(s) may be deposited onto the surface of the treated carbonsupport before, simultaneously with, or after deposition of the noblemetal onto the surface. Methods to deposit a promoter metal aregenerally known in the art, and include the methods noted aboveregarding noble metal deposition.

After the carbon support has been impregnated with the noble metal(s)and optional promoter(s), the surface of the catalyst is preferablyheated to elevated temperatures, for example, in a heat treatment orcalcining operation. For example, calcining may be carried out byplacing the catalyst in a kiln (e.g., rotary kilns, tunnel kilns, andvertical calciners) through which a heat treatment atmosphere is passed.

Generally, the surface of the treated support impregnated with one ormore metals is heated to a temperature of at least about 700° C., atleast about 800° C., at least about 850° C., at least about 900° C., orat least about 950° C. Typically, the metal-impregnated support isheated to a temperature of from about 800° C. to about 1200° C.,preferably from about 850° C. to about 1200° C., more preferably fromabout 900° C. to about 1200° C., even more preferably from about 900° C.to about 1000° C. and especially from about 925° C. to about 975° C.

The period of time that the impregnated support is subjected to elevatedtemperatures (including the time at which the support is heated at themaximum temperature) is not narrowly critical. Typically, in commercialscale apparatus, the metal-impregnated support is heated at the maximumheat treatment temperature for at least about 10 minutes (e.g., at leastabout 30 minutes).

Preferably, the metal-impregnated support is heated in a non-oxidizingenvironment. The non-oxidizing environment may comprise or consistessentially of inert gases such as N₂, noble gases (e.g., argon, helium)or mixtures thereof. In certain embodiments, the non-oxidizingenvironment comprises a reducing environment and includes a gas-phasereducing agent such as, for example, hydrogen, carbon monoxide, orcombinations thereof. The non-oxidizing environment in which thecatalyst is heated may include other components such as ammonia, watervapor, and/or an oxygen-containing compound as described, for example,by Wan et al. in International Publication No. WO 2006/031938. In oneembodiment, heat treatment following metal deposition preferablycomprises high-temperature gas-phase reduction to removeoxygen-containing functional groups from the surface of the catalyst,thereby attaining a catalyst exhibiting the carbon monoxide desorptionand/or carbon atom to oxygen atom surface ratio characteristics asdescribed in Ebner et al. U.S. Pat. No. 6,417,133.

In various preferred embodiments, the noble metal is alloyed with atleast one promoter to form alloyed metal particles. For example, noblemetal particles at a surface of the carbon support may comprise noblemetal atoms alloyed with promoter metal atoms. In various otherpreferred embodiments, the noble metal is alloyed with two promoters(e.g., iron and cobalt). Catalysts comprising a noble metal alloyed withone or more promoters often exhibit greater resistance to metal leachingand further stability (e.g., from cycle to cycle) with respect toformaldehyde and formic acid oxidation. It is to be understood that theterm alloy as used herein generally encompasses any metal particlecomprising a noble metal and at least one promoter (e.g., intermetalliccompounds, substitutional alloys, multiphasic alloys, segregated alloys,and interstitial alloys as described by Wan et al. in InternationalPublication No. WO 2006/031938).

Subjecting the metal-impregnated support to heat treatment generallyprovides agglomeration and/or sintering of metal particles at thesurface of the support. Utilizing treated substrates having blockedmicropores results in impregnated supports having a reduced proportionof relatively small metal-containing particles at the support surfacewithin the micropore domain, which are generally more susceptible toleaching and/or deactivation, as compared to larger-sized noblemetal-containing particles. Additionally or alternatively,metal-containing particles at the substrate surface outside themicropore domain are generally more accessible to reactants. By virtueof either or both of these effects, treated substrates of the presentinvention are believed to provide more efficient metal usage (e.g., anincrease in effective catalytic metal surface area per unit weight) inthe catalyst.

It is to be noted that persistence of the pore blocker in the treatedsubstrate following post-metal deposition heat treatment is not criticalto provide the above-noted advantages. In fact, it is currently believedthat the pore blocker is most likely decomposed and/or otherwise removedfrom the substrate surface during calcining. But it is further currentlybelieved that one or more of the above-noted advantages are achieved solong as the pore blocker is preferentially retained with the selectedpores at the support surface during metal deposition in order to promotethe desired metal dispersion.

E. Catalysts Prepared Using Treated Substrates

Substrates treated in accordance with the present method (i.e., poreblocked substrates) may be utilized as supports for metal-containingcatalysts including, for example, catalysts including one or more noblemetals (e.g., a noble metal such as platinum) deposited on a particulatecarbon support. In addition, noble metal-containing catalysts preparedusing substrates treated by the present invention may include one ormore promoter(s) and may be prepared in a manner to exhibit one or moreof the properties as described, for example, in U.S. Pat. No. 6,417,133,International Publication No. WO 2006/031938, and U.S. Pat. No.6,956,005, the entire contents of which are incorporated herein byreference for all relevant purposes.

Generally, the noble metal constitutes less than about 8% by weight ofthe catalyst, typically less than about 7% by weight of the catalyst,more typically less than about 6% by weight of the catalyst. In variousembodiments, the noble metal typically constitutes from about 1% toabout 8% by weight of the catalyst, more typically from about 2% toabout 7% by weight of the catalyst and, still more typically, from about3% to about 6% by weight of the catalyst.

As noted, particulate carbon supports treated in accordance with thepresent invention to preferentially block micropores provide moreefficient metal usage. Accordingly, effective catalysts may be preparedthat contain noble metal in an amount below the above-noted limitsand/or at or near the lower limits of one or more of the above-notedranges. For example, in various embodiments, the noble metal constitutesless than about 5% by weight of the catalyst, less than about 4% byweight of the catalyst, or even less than about 3% by weight of thecatalyst. By way of further example, in various embodiments the noblemetal typically constitutes from about 1% to about 5% by weight of thecatalyst, more typically from about 1.5% to about 4% by weight of thecatalyst and, still more typically, from about 2% to about 3% by weightof the catalyst. However, it should be understood that the presentinvention does not require that a treated substrate be used forpreparation of a noble metal-containing catalyst including a reducedproportion of noble metal as compared to conventional catalysts. Namely,preparation of a catalyst including a treated porous substrate thatprovides more efficient metal usage at conventional noble metal loadingslikewise represents an advance in the art (e.g., treated substrates ofthe present invention are currently believed to provide a reducedproportion of relatively small metal particles that are susceptible toleaching and represent inefficient metal usage, thereby contributing toimprovements in catalytic activity and reduced undesired by-product(e.g., IDA) formation).

Generally, in accordance with some embodiments, at least one promoter(e.g., iron) constitutes less than about 2% by weight of the catalyst,less than about 1.5% by weight of the catalyst, less than about 1% byweight of the catalyst, less than about 0.5% by weight of the catalyst,or about 0.4% by weight of the catalyst. Typically, at least onepromoter constitutes less than about 1% by weight of the catalyst,preferably from about 0.25% to about 0.75% by weight of the catalystand, more preferably, from about 0.25% to about 0.6% by weight of thecatalyst. In various preferred embodiments, the catalyst includes ironas a promoter. Additionally or alternatively, the catalyst includescobalt as a promoter.

In various particularly preferred embodiments, the catalyst comprisesboth iron and cobalt promoters. Use of iron and cobalt generallyprovides benefits associated with use of iron (e.g., activity andstability with respect to formaldehyde and formic acid oxidation).However, as compared to the presence of iron alone as a promoter, thepresence of cobalt tends to reduce formation of certain by-productsduring oxidation of a PMIDA substrate (e.g., IDA). Moreover, IDAformation is believed to be directly related to total iron content ofthe catalyst. Thus, in various iron/cobalt co-promoter embodiments, ironcontent is essentially replaced by cobalt to reduce formation of IDA andother by-products while nevertheless providing sufficient activitytowards oxidation of formaldehyde and formic acid. For example, ascompared to a platinum on carbon catalyst containing 0.5% by weight ironin the absence of cobalt, a similar catalyst containing 0.25% by weightiron and 0.25% by weight cobalt typically provides comparable activityfor PMIDA, formaldehyde and formic acid oxidation, while minimizingby-product formation.

In iron/cobalt co-promoter embodiments, the amount of each promoter atthe surface of the carbon support (whether associated with the carbonsurface itself, noble metal, or a combination thereof) is typically atleast about 0.05% by weight, at least about 0.1% by weight or at leastabout 0.2% by weight. Furthermore, the amount of iron at the surface ofthe carbon support is typically from about 0.1 to about 4% by weight ofthe catalyst, preferably from about 0.1 to about 2% by weight of thecatalyst, more preferably from about 0.1 to about 1% by weight of thecatalyst and, even more preferably, from about 0.1 to about 0.5% byweight of the catalyst. Similarly, the amount of cobalt at the surfaceof the carbon support is typically from about 0.1 to about 4% by weightof the catalyst, preferably from about 0.1 to about 2% by weight of thecatalyst, more preferably from about 0.2 to about 1% by weight of thecatalyst and, even more preferably, from about 0.2 to about 0.5% byweight of the catalyst. In such an embodiment, the weight ratio of ironto cobalt in the catalyst is generally from about 0.1:1 to about 1.5:1and preferably from about 0.2:1 to about 1:1. For example, the catalystmay comprise about 0.1% by weight iron and about 0.4% by weight cobaltor about 0.2% by weight and about 0.2% by weight cobalt.

As understood by those skilled in the art, the metal content of thecatalysts can be freely controlled within the ranges described herein(e.g., by adjusting the concentration and relative proportions of themetal source(s) used in a liquid phase reactive deposition bath).

II. First and Second Metal-Containing Catalysts

Various preferred embodiments of the present invention are directed tocatalysts that comprise and/or are prepared from a porous substrate orsupport having one or more regions of a first metal at its surface, anda second metal at the surface of the one or more regions of the firstmetal. In such embodiments, the first metal is selected to have anelectropositivity greater than the electropositivity of the second metal(i.e., the first metal is higher than the second metal in theelectromotive series). Oxidation of the first metal provides electronsfor reduction of second metal ions present in the deposition bath tothereby deposit second metal atoms at the surface of the one or moreregions of the first metal. The first metal oxidation and second metalreduction and deposition occur substantially simultaneously and secondmetal atoms are deposited at the surface of the one or more regions ofthe first metal by displacement of first metal ions from the one or moreregions into the deposition bath. Metal deposition in this manner may bereferred to as spontaneous, or redox displacement deposition. (See, forexample, U.S. Pat. No. 6,670,301 to Adzic et al. and U.S. Pat. Nos.6,376,708, 6,706,662 and 7,329,778 to Morgenstern et al.) Preferably,the sacrificial first metal is less expensive than the second metal.

As detailed herein, deposition of the second metal by displacementdeposition is preferably conducted and controlled in a manner thatprovides preferential deposition of the second metal at the surface ofthe one or more regions of the first metal. That is, the second metal ispreferentially deposited at the surface of the first metal region(s) bydisplacement deposition over deposition of the second metal at thesupport surface and/or deposition of the second metal at the surface ofalready-deposited second metal.

Without being bound to a particular theory, it is currently believedthat the source of second metal ions may promote preferential depositionof the second metal onto the one or more regions of first metal. Moreparticularly, it is currently believed that second metal sources thatprovide second metal ions at lower oxidation numbers (e.g., +2) provideslower, more controlled metal deposition as compared to sources thatprovide noble metal ions at higher oxidation numbers (e.g., +4). Secondmetal ions at such higher oxidation numbers are believed to be morereadily reduced in the presence of electrons generated by oxidation ofthe first metal which provides a greater driving force for deposition ofthe second metal. This greater driving force is believed to increase therate of second metal deposition which, in turn, is believed to promoteless discriminate deposition of the second metal. More particularly, thegreater driving force for deposition of second metal ions is believed topromote deposition of second metal atoms onto the support and/or ontothe surface of already-deposited second metal atoms. Accordingly, it iscurrently believed that as the oxidation state of second metal ionsdecreases, preferential (e.g., selective) deposition of the noble metaldirected onto one or more regions of first metal by displacement offirst metal atoms over deposition onto the carbon support and/oralready-deposited second metal atoms generally increases.

In addition, it is currently believed that deposition of second metalatoms utilizing sources that provide ions at relatively low oxidationnumbers proceeds in a manner that generally reduces the complexity ofthe displacement deposition process to promote the desired preferentialdeposition of the second metal directed onto the first metal regions.For example, displacement deposition utilizing sources that providesecond metal ions at relatively low oxidation numbers proceeds readilyin the absence of precise control of concentration of the second metalsource and/or deposition time.

In accordance with the present invention, it is currently believed thata significant fraction, if not substantially all, of the second metaldeposited by controlled displacement of a first metal provides domainsor regions at the surface of one or more regions of the first metalcharacterized as comprising a relatively thin layer of second metalatoms (e.g., no more than about 5 atoms thick, or no more than about 3atoms thick), rather than agglomerating to form metal-containingparticles. In certain preferred embodiments, preparation of the catalystby the present method may provide a near monolayer of second metal(e.g., a layer of second metal atoms no more than about 3 atoms inthickness, no more than about 2 atoms in thickness, and preferably fromabout one to about two atoms in thickness).

Further in accordance with the present invention, it is currentlybelieved that deposition of the second metal by displacement of firstmetal atoms from one or more regions of first metal provides a structure(e.g., a catalyst precursor structure) that, upon heat treatment atelevated temperatures, provides metal particles that include the secondmetal in a form that represents more efficient second metal utilization.In various embodiments, the metal particles are typically firstmetal-rich (i.e., contain an excess of first metal atoms over secondmetal atoms) and it is currently believed that the particles include oneor more bimetallic alloys. In contrast, conventional noblemetal-containing catalysts typically include particles comprising anatomic excess of noble metal atoms. In this manner, the first metal-richparticles are believed to include the noble (i.e., second) metal in aform that represents a reduced proportion of noble metal distributedthroughout the particle and, accordingly, represents reduced unexposed,and potentially unutilized noble metal atoms throughout the particlestructure. But an excess of first metal is not required to provide animprovement in metal utilization. However, to the extent that theproportion of first metal to second metal is increased, improvements insecond metal utilization may be realized. Accordingly, variousembodiments of the present invention contemplate selecting first andsecond metal combinations that are amenable to forming alloys thatinclude at least an equivalent atomic proportion of first metal (M₁) tosecond metal (M₂). More particularly, in various embodiments there is apreference for selecting first and second metal combinations thatprovide bimetallic alloys of first and second metal, M_(1x)M_(2y), wherethe atomic ratio of x:y is greater than or equal to 1. Further inaccordance with these and various other preferred embodiments, the metalparticles include bimetallic alloys in which the atomic ratio of x:y isgreater than about 2, or greater than about 3. For example, in the caseof copper and platinum first and second metals, respectively, the metalparticles at the surface of the support may include CuPt and/or Cu₃Ptbimetallic alloys. By way of further example, in the case of tin andplatinum first and second metals, respectively, at least some of themetal particles may include Pt₂Sn₃, PtSn₂, and/or PtSn₄ bimetallicalloys. In the case of iron and platinum first and second metals,respectively, the metal particles at the surface of the support mayinclude, for example, Fe₃Pt, FePt, Fe_(0.75)Pt_(0.25).

Additionally or alternatively, it is also currently believed that atleast some of the supported metal particles produced upon calcination ofa catalyst precursor structure prepared by displacement deposition of anoble (i.e., second) metal as detailed herein include a relatively thinlayer or shell comprising second metal atoms (e.g., a layer of secondmetal atoms no more than about 3 atoms thick) at least partiallysurrounding a core comprising the first metal. The core generallycomprises a relatively high concentration of first metal (e.g., greaterthan about 50 atom percent). The combination of a first metal-rich coreand second metal-containing shell provides a relatively low proportionof unexposed second metal and, thus, provides improvements in exposedmetal surface area per unit metal weight. It is currently believed thatparticles exhibiting such a core-shell arrangement may generally providea greater improvement in second metal utilization over conventionalsupported noble metal catalysts as compared to particles generallycharacterized as first metal-rich (i.e., a greater increase in exposedsecond metal surface area per unit second metal weight). Thus, as thefraction of core-shell particles at the surface of the supportincreases, metal utilization in the catalyst likewise increases.Accordingly, in various preferred embodiments, the catalyst includes apredominant fraction of metal particles exhibiting a core-shellarrangement. However, it is to be noted that improvements in metalutilization are nonetheless provided by virtue of the presence of metalparticles generally rich in first metal content, regardless of thepresence of any particles characterized as exhibiting a core-shellarrangement.

It is to be noted that reference to a porous substrate such as a carbonsupport having first and second metals deposited thereon (i.e., a firstand second metal-containing support) as a catalyst precursor structuredoes not exclude catalytic activity of these impregnated supports in theabsence of subsequent heat treatment. In fact, experimental evidenceindicates that metal-impregnated supports prepared in this manner mayfunction as effective catalysts. Accordingly, elsewhere herein(including the claims) porous substrates having a first metal depositedthereon (e.g., a first metal-impregnated support) are likewise referredto as catalyst precursor structures. But in various preferredembodiments, the first and second metal-impregnated support is heated atelevated temperatures to provide the catalyst (sometimes referred toherein as a finished catalyst).

Experimental evidence indicates that catalysts (i.e., both catalystprecursor structures and finished catalysts) prepared as detailed hereinutilizing a noble metal and a first, sacrificial metal layer are atleast as active as conventional noble metal on carbon catalysts on a perunit metal weight basis. Without being bound to a particular theory, itis currently believed that active sites or domains of second metalprovided by the method of the present invention provide an increase incatalytic surface area per unit metal weight as compared to conventionalmetal-containing catalysts prepared by methods that do not includedisplacement deposition of the second metal onto one or more regions ofa first, sacrificial metal.

Conventional noble metal on carbon catalysts generally include noblemetal-containing particles at the surface of the support formed byagglomeration and/or sintering of noble metal atoms and/or noblemetal-containing particles. This agglomeration typically occurs duringpost-deposition heat treatment of a noble metal-impregnated support atrelatively high temperatures. Metal particles of conventional noblemetal catalysts formed by agglomeration of deposited metal at thesurface of a support, typically include the noble metal distributedthroughout the entire particle (e.g., the particles exhibit acomposition profile of relatively constant noble metal concentrationthroughout). Particle stability (e.g., resistance to leaching and/ordeactivation under reaction conditions) generally increases withincreased particle size, but exposed metal catalytic surface area perunit metal weight typically decreases in larger particles. Thus, despitethe increased stability, an abundance of relatively large noblemetal-containing particles and the attendant lower catalytic metalsurface area per unit metal weight represents less efficient metalusage. Advantageously, first metal-rich particles and/or metal particlescomprising a noble (i.e., second) metal-containing shell and firstmetal-containing core prepared in accordance with various embodiments ofthe present invention generally represent more efficient metal usage.For example, as noted, the first metal-rich particles are believed toinclude the second metal in a form (e.g., a bimetallic alloy includingan atomic excess of first metal) that provides a reduced proportion ofunexposed second metal.

Additionally or alternatively, and as detailed elsewhere herein, larger,more stable metal particles in accordance with the present invention arenot associated with an unacceptable decrease in effective catalyticsecond metal surface area since an increase in particle size isgenerally associated with an increase in the size of the firstmetal-rich core. For example, experimental evidence indicates relativelyconstant thickness of the second metal-containing shell over a range ofparticle sizes. Accordingly, as particle size increases, the fraction(atom and/or weight) of the particle provided by the first metal-richcore generally increases while the fraction of the particle provided bythe second metal-containing shell generally decreases. However, theexposed second metal surface area increases with increased particlesize. For example, as compared to a particle including a core 1 nm indiameter, at constant second metal shell thickness, a particle includinga core 10 nm in diameter may provide up to a 100-fold increase inexposed surface area of the second metal-containing shell.

One mechanism for deactivation of conventional noble metal on carboncatalysts prepared by deposition of noble metal in the absence of asacrificial metal involves over-oxidation of platinum as a result ofcharge build-up among the active sites comprising particles ofagglomerated noble metal atoms. It is currently believed thatmetal-containing particles in which a second metal-containing shell atleast partially surrounds a first metal-containing core result inreduced over-oxidation of the catalyst. In this manner, the form of thecatalyst provides an improvement in activity. With regard to a catalystprecursor structure, it is currently believed that preferentialdeposition of second metal by displacement of first metal to formdomains or active sites less prone to agglomeration to formmetal-containing particles than metal deposited in the absence of asacrificial metal provides greater dispersion of charge among the activesites and, thus, reduced catalyst deactivation by over-oxidation of themetal.

It is to be noted that a certain degree of agglomeration of second metalto form primarily second metal-containing particles may occur in firstand second metal-containing catalysts prepared in accordance with thepresent invention. However, it is currently believed that any suchagglomeration occurs to a lesser extent than observed in catalystsprepared without a first, sacrificial metal and, in any event, secondmetal agglomeration is not believed to occur to any significant degreethat prevents achieving the above-noted benefits of improved metalutilization.

It is also currently believed that the above-described methods utilizinga first, sacrificial metal layer may be utilized in conjunction with themethods for treating porous substrates detailed elsewhere herein. Forexample, a first metal may be deposited onto a porous support firsttreated in accordance with the methods detailed herein (e.g., asubstrate having a pore blocking compound disposed and/or preferentiallyretained within its micropores), followed by deposition of a secondmetal onto one or more regions of the deposited first metal. In thismanner, it is currently believed that deposition of both the one or moreregions of the first metal, and subsequent deposition of the secondmetal thereon are preferentially directed outside the relatively smallpore (e.g., micropore) domain of the substrate, thereby providingadvantageous dispersion of the first and second metals and contributingto one or more of the above-noted benefits with respect to metalutilization.

A. First Metal

In those embodiments of the present invention in which the catalyst orprecursor includes one or more regions of a first metal at the surfaceof the support, the first metal is generally selected from the groupconsisting of vanadium, tungsten, molybdenum, gold, osmium, iridium,tantalum, palladium, ruthenium, antimony, bismuth, arsenic, mercury,silver, copper, titanium, tin, lead, germanium, zirconium, cerium,nickel, cobalt, iron, chromium, zinc, manganese, aluminum, beryllium,magnesium, lithium, barium, cesium, and combinations thereof. In variouspreferred embodiments, the first metal is selected from the groupconsisting of copper, iron, tin, nickel, cobalt, and combinationsthereof. In various other preferred embodiments, the first metalcomprises copper, tin, nickel, or a combination thereof. In variousother preferred embodiments, the first metal is tin or the first metalis copper. In still further embodiments, the first metal comprisescobalt, copper, iron and combinations thereof. In various preferredembodiments, the first metal is copper. In various other preferredembodiments, the first metal is iron. In still further preferredembodiments, the first metal is cobalt.

Generally, the support is contacted with a deposition bath comprisingions of the first metal and one or more other components to deposit thefirst metal at the surface of the support. At least two events occurduring deposition of the first metal at the surface of the support: (1)nucleation (i.e., deposition of first metal atoms at the surface of thesupport) and (2) particle growth (i.e., agglomeration of deposited firstmetal atoms). As used herein, the term region(s) of first metal refersto a group of agglomerated first metal atoms at the surface of thesupport. It is currently believed that the sizes, or dimensions of theseregions (i.e., the proportion of support surface area over which aregion of first metal is deposited) may directly impact theeffectiveness/suitability of the catalyst.

For example, the proportion of deposition, or exchange sites for secondmetal deposition decreases along with decreasing dimensions of firstmetal regions. In addition, resistance to leaching and/or deactivationunder reaction conditions generally decreases as one or more dimensionsof the first metal region size decrease. Thus, it is preferred that thedimensions of the first metal regions are sufficiently resistant tometal leaching and provide a sufficient proportion of sites for secondmetal deposition. Accordingly, one or more conditions of first metaldeposition are preferably controlled to provide a suitable balancebetween nucleation and agglomeration (i.e., particle growth) and, thus,provide first metal regions of suitable dimensions that providesufficient exchange sites for deposition of second metal, are stablethemselves and, thus, promote deposition of stable domains, or regionsof second metal. For example, as detailed elsewhere herein, first andsecond metal-containing supports preferably include an excess of firstmetal, which contributes to providing the second metal in a form thatpromotes more efficient metal utilization.

In addition to achieving a desirable balance between nucleation andagglomeration, the location, or dispersion of the one or more regions offirst metal at the support surface may impact metal utilization. Thatis, the considerations noted above generally concerning deposition ofmetal among relatively small pores generally likewise apply todeposition of one or more first metal regions and the dispersion ofthese regions among the pores of porous substrates is currently believedto affect catalyst performance. Accordingly, one or more conditions offirst metal deposition are generally controlled and/or selected toprovide a desired dispersion of first metal regions. Thus, generally,conditions of first metal deposition preferably promote deposition ofthe first metal at the support surface to provide regions of first metalat the support having one or more dimensions that provide a suitableproportion of exchange sites for deposition of second metal at thesurface of the first metal regions. More particularly, it is currentlybelieved that the dimensions of the first metal regions preferablyprovide a suitable excess of deposited first metal with respect to thedesired proportion of second metal to be deposited. For example, asdetailed elsewhere herein, supports having first and second metalsdeposited thereon in accordance with the present invention may becharacterized by a minimum atom ratio of first metal to second metal.

1. Coordinating Agents/Pore Blocking

In various preferred embodiments, preferential deposition of the firstmetal outside relatively small pores (e.g., the micropore domain) of thesubstrate may be promoted by the presence of one or more components ofthe first metal deposition bath. More particularly, dispersion of firstmetal in this manner may be promoted by the presence of one or morecomponents of the deposition bath referred to herein as coordinatingagent(s).

It is currently believed that a component of the first metal depositionbath may function as a coordinating agent by forming one or morecoordination bonds with the first metal and that the thus formedcoordination compound may be unable to enter certain relatively smallpores of the substrate, thereby preventing coordinated first metal fromdepositing among those portions of the substrate surface. It is to beunderstood that the precise form of any coordination bond(s) between thecompound and metal, or the precise form of any coordination compoundthus formed are not narrowly critical. However, it is currently believedthat a coordination compound generally includes an association or bondbetween the first metal ion and one or more binding sites of one or moreligands. The coordination number of a metal ion of a coordinationcompound generally corresponds to the number of other ligand atomslinked thereto. Ligands may be attached to the central metal ion by oneor more coordinate covalent bonds in which the electrons involved in thecovalent bonds are provided by the ligands (i.e., the central metal ioncan be regarded as an electron acceptor and the ligand can be regardedas an electron donor). The typical donor atoms of the ligand include,for example, oxygen, nitrogen, and sulfur. The ligands can provide oneor more potential binding sites; ligands offering two, three, four,etc., potential binding sites are termed bidendate, tridendate,tetradentate, etc., respectively. Just as one central atom cancoordinate with more than one ligand, a ligand with multiple donor atomscan bind with more than one central atom. Coordinating compoundsincluding a metal ion bonded to two or more binding sites of aparticular ligand are typically referred to as chelates.

Additionally or alternatively, a coordinating agent as described hereinmay promote dispersion of the first metal at the support surface byvirtue of the coordination bonds between the coordinating agent andmetal to be deposited retarding or delaying reduction of the metal ionsand metal deposition at the support surface while promoting dispersionof the first metal over the support surface. The strength ofcoordination between the coordinating agent and metal generallyinfluences the effectiveness of the agent for promoting dispersion ofthe first metal over the support surface. Unless the strength ofcoordination reaches a minimum threshold, the effect of the agent ondispersion will not be noticeable to any significant degree and thedegree of coordination that prevails in the deposition bath willessentially mimic water solvation. As the strength of coordinationbetween the agent and metal increases, a greater concentration ofreducing agent may be utilized and/or a relatively strong reducing agent(e.g., metal hydride) may be included in the deposition bath to promotereduction of the coordination complex and/or first metal reduction anddeposition. Coordinating agent and/or ligand(s) derived therefrompresent in the deposition bath may effectively function as a poreblocking compound during and/or after first metal deposition. Forexample, once the coordination bond(s) between the first metal and thecoordinating agent have been broken, the agent or ligand(s) may bedisposed within micropores of the support.

In accordance with the foregoing regarding deposition bath componentsthat may function as coordinating agents, in these and various otherpreferred embodiments, such components of the first metal depositionbath may promote desirable dispersion of the one or more regions offirst metal by virtue of a pore blocking function. That is, in additionto preventing entry of coordinated first metal into certain pores of thesubstrate, components of the first metal deposition bath described ascoordinating agents may themselves be deposited among certain,relatively small pores of the porous substrate, thereby inhibiting, andpreferably substantially preventing, deposition of first metal withinthe relatively small pores. Generally, these compounds are believed tofunction as pore blocking compounds during first metal deposition andthat preferential deposition of first metal and pore blocking may occursubstantially simultaneously to provide a first metal-impregnatedsubstrate.

But it is to be understood that treating a porous substrate inaccordance with the methods detailed above to dispose within and/orintroduce a pore blocking compound into pores of the substrate, followedby metal deposition, likewise provides suitable substrates.

A variety of compounds that function as coordinating agents and/or poreblocking compounds may be included in the first metal deposition bath toprovide one or more of the above-noted effects. Generally, thesecompounds are selected from the group consisting of various sugars, 5-or 6-member ring-containing compounds (e.g., 1,3- and 1,4-disubstitutedcyclohexanes), polyols, Rochelle salts, acids, amines, citrates, andcombinations thereof. For example, the compound may be selected from thegroup consisting of sucrose, sorbitol, mannitol, xylitol, Rochelle salts(potassium sodium tartrates), ethylenediaminetetraacetic acid (EDTA),N-hydroxyethylethylenediaminetetraacetic acid (HEDTA), nitrilotriaceticacid (NTA), N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine, andcombinations thereof.

It is to be noted that the advantageous effects provided by the presenceof these compounds referred to herein as coordinating agents or poreblockers are based in part on experimental evidence. While it iscurrently believed that one or more of these compounds provide either orboth of the coordinating and pore blocking functions, it should beunderstood that the present invention is not dependent on either or bothof these theories and does not require one or more compounds providingeither or both of these functions.

In various preferred embodiments (e.g., those in which the first metalis copper or iron), the deposition bath comprises sucrose that isbelieved to function as a coordinating agent and/or pore blockingcompound. In addition to these effect(s) in accordance with thepreceding discussion, its presence may offer other advantages. Forexample, as detailed elsewhere herein, first metal deposition mayproceed more readily at higher pH. The coordinating effect of sucroseallows for deposition of the first metal at higher pH since thecoordinating effect reduces the risk of excessive first metalprecipitation at higher pH.

Generally, the coordinating agent/pore blocker, or a combination ofagents/blockers, is present in the first metal deposition bath at aconcentration of at least about 10 g/L, at least about 20 g/L, or atleast about 30 g/L. Preferably, this component of the first metaldeposition bath is present at a concentration of from about 10 g/L toabout 115 g/L, from about 25 g/L to about 100 g/L, or from about 40 g/Lto about 85 g/L. Further in accordance with these and various otherpreferred embodiments, the weight ratio of coordinating agent to firstmetal in the deposition bath is generally at least about 3:1, typicallyat least about 5:1 and, more typically, at least about 8:1. For example,generally the weight ratio of coordinating agent to first metal in thedeposition bath is generally from about 3:1 to about 20:1, typicallyfrom about 5:1 to about 15:1 and, more typically, from about 8:1 toabout 12:1.

2. Electroless Plating of First Metal

Generally and in accordance with the foregoing, deposition of firstmetal at the surface of the support may be conducted in accordance withconventional methods known in the art. Thus, typically first metaldeposition is conducted by electroless plating in which the support iscontacted with a deposition bath generally comprising a source of thefirst metal in the absence of an externally applied voltage. Thedeposition bath generally comprises a reducing agent that reduces ionsof the first metal to form metal atoms that are deposited at the surfaceof the support.

Generally, the source of the first metal is a first metal saltincluding, for example, first metal sulfates, first metal nitrates,first metal chlorides, first metal tartrates, first metal phosphates,and combinations thereof. The concentration of first metal in thedeposition bath is generally selected in view of the desired first metalcontent. Typically, the source of first metal is present in thedeposition bath at a concentration of at least about 0.25 g/L, at leastabout 1 g/L, at least about 2.5 g/L, or at least about 4 g/L. Forexample, the first metal source may be present in the deposition bath ata concentration of from about 1 to about 20 g/L, from about 2.5 to about12.5 g/L, or from about 4 to about 10 g/L.

3. Copper Deposition

The following discussion focuses on deposition of copper as the firstmetal onto a porous carbon support. However, as detailed elsewhereherein, it should be understood that the present invention likewisecontemplates deposition of first metals other than copper onto carbonsupports, and deposition of copper and other first metals ontonon-carbon supports.

(a) Sources of Copper

Sources of copper ions suitable for use in the methods of the presentinvention include copper salts such as the nitrate, sulfate, chloride,acetate, oxalate, and formate salts of copper, and combinations thereof.Salts containing copper in the divalent state (i.e., Cu(II)) aregenerally preferred including, for example, copper sulfate.

(b) Copper Loading in Deposition Bath

First metal loading in the deposition bath may affect the quality (e.g.,resistance to leaching) and/or suitability (e.g., dispersion of firstmetal over a sufficient portion of support surface) of first metaldeposition. More particularly, the relative proportions of first metaland support are currently believed to impact first metal deposition.Agglomeration, or particle growth, and the dimensions of the resultingregions of first metal may increase with increased copper loading. Asnoted above, the dimensions of the first metal regions are preferablycontrolled to promote a suitable balance between dispersion andstability of the first and second metals. Accordingly, the concentrationof copper in the deposition bath satisfies the above-noted limits and/oris within the above-noted ranges.

For example, typically copper is present in the first metal depositionbath at a concentration of at least about 0.25 g/L, more typically atleast about 1 g/L, still more typically at least about 2 g/L, and evenmore typically at least about 3 g/L (e.g., at least about 5 g/L).Preferably, copper is present in the first metal deposition bath at aconcentration of from about 0.25 to about 15 g/L, more preferably fromabout 1 to about 12 g/L and, still more preferably, from about 2 toabout 10 g/L.

(c) Reducing Agents

Suitable reducing agents include those generally known in the artincluding, for example, sodium hypophosphite (NaH₂PO₂), formaldehyde(CH₂O) and other aldehydes, formic acid (HCOOH), salts of formic acid,salts of borohydride (e.g., sodium borohydride (NaBH₄)), salts ofsubstituted borohydrides (e.g., sodium triacetoxyborohydride(Na(CH₃CO₂)₃BH)), sodium alkoxides, hydrazine (H₂NNH₂), and ethyleneglycol. In various preferred embodiments, formaldehyde is the preferredreducing agent. For copper deposition in non-aqueous deposition baths,gaseous hydrogen is often the preferred reducing agent since it isgenerally readily soluble in organic solvents.

The manner of addition of reducing agent to the deposition bath is notnarrowly critical, but in various embodiments the reducing agent isadded at a relatively slow rate (e.g., over a period of from about 5minutes to 3 hours, or over a period of from about 15 minutes to about 1hour) to a slurry of the support and first metal in water or an alcoholand under an inert atmosphere (e.g., N₂). If the reducing agent isinstead first added to the copper salt, it preferably may be added to asolution which contains the copper salt and also a coordinating agent(e.g., chelator). The presence of the chelator inhibits the reduction ofthe copper ions before the copper-salt solution is combined with thesupport and which, as detailed herein, may likewise promote advantageousdeposition of first metal throughout the surface of the support.

Typically, in the case of formaldehyde as the reducing agent, thereducing agent is present in the first metal deposition bath at aconcentration of at least about 1 g/L, more typically at least about 2g/L and, still more typically, at least about 5 g/L. For example, in thecase of formaldehyde as the reducing agent, preferably formaldehyde ispresent in the deposition bath at a concentration of from about 1 toabout 20 g/L, more preferably from about 2 to about 15 g/L and, stillmore preferably, from about 5 to about 10 g/L.

Additionally or alternatively, in the case of a formaldehyde reducingagent, generally formaldehyde and the first metal (e.g., copper) arepresent in the deposition bath at a weight ratio of formaldehyde tofirst metal of at least about 0.5:1, and typically at least about 1:1.For example, in various embodiments, the weight ratio of formaldehyde tofirst metal in the deposition bath is from about 0.5:1 to about 5:1,from about 1:1 to about 3:1, or from about 1:1 to about 2:1.

(d) Temperature

The temperature of the deposition bath may affect nucleation andagglomeration (e.g., particle growth) that occur during first metaldeposition. For example, generally nucleation (i.e., metal deposition)and agglomeration increase with increasing deposition bath temperature.

Thus, preferably the temperature of the deposition bath does not reach alevel that promotes metal agglomeration and/or metal leaching underreaction conditions to an undesired degree. Reducing the temperature ofthe plating bath generally suppresses nucleation to a greater degreethan agglomeration. Accordingly, the temperature of the plating bath ispreferably high enough so that nucleation is not retarded to anunacceptable degree. In accordance with the present invention, it iscurrently believed that first metal deposition baths having atemperature of from about 5° C. to about 60° C. generally address theseconcerns and provide suitable deposition of the first metal. Preferably,the temperature of the first metal deposition bath is from about 10° C.to about 50° C.; more preferably, the temperature of the first metaldeposition bath is from about 20° C. to about 45° C. It is to be notedthat reference to the temperature of the first metal deposition bath mayrefer to the temperature of the bath prior to and/or during contact ofthe deposition bath and the support.

(e) Agitation

Preferably the first metal deposition bath is agitated to promotedispersion of the first metal over the surface of the support. Agitationmay also promote diffusion of the reducing agent throughout the support.Experimental evidence indicates that sufficient agitation may contributeto improvements in catalytic activity. However, excessive agitation ofthe deposition bath may cause dispersion of copper to a degree thatprovides first metal regions that may be less resistant to leaching thanless dispersed regions. For example, undesirably high dispersion mayresult in deposition of a portion of first metal within the relativelysmall pores of the support that is less prone to agglomeration to formfirst metal regions generally resistant to leaching.

In addition, it is currently believed that the type of agitator mayimpact deposition of the first metal. Experimental evidence indicatesthat the first metal (e.g., copper) may deposit onto the agitatorsurface resulting in reduced first metal deposition onto the carbonsupport and, therefore, reduced sites for deposition of second metal.For example, first metal may deposit onto the surface of agitators thatinclude or are constructed of metal (e.g., coated metal agitators).Thus, in various preferred embodiments, the agitator is constructed ofmaterial that generally prevents, and preferably substantiallycompletely prevents first metal deposition at the surface of theagitator. For example, the agitator may preferably be constructed ofglass, or various other materials that preferably avoid first metaldeposition at the agitator surface.

(f) Deposition pH

Copper deposition is generally more effective at higher pH (e.g.,greater than about 8, greater than about 9, or greater than about 10).In fact, as deposition bath pH increases, copper deposition throughreduction and precipitation onto the support may proceed at a rate thatmay hinder sufficient dispersion of the first metal over the supportsurface. In addition to the above-noted benefits, the presence of acoordinating agent such as sucrose is currently believed to retardcopper precipitation at high pH and thereby promote sufficientdispersion of the metal over the surface of the support. Formation of acoordination complex between the first metal and a coordinating agent isgenerally enhanced at the above-noted pH levels. However, at certainlevels the pH of the deposition bath may negatively impact solvation offirst metal ions and first metal reduction and deposition. Accordingly,in various preferred embodiments in which a coordinating agent ispresent in the deposition bath, the pH of the deposition bath is fromabout 8 to about 13, or from about 9 to about 12.

4. Iron Deposition

In various preferred embodiments, the first metal is iron. Generally,deposition of iron at the surface of the support may be conducted inaccordance with conventional methods known in the art (e.g., electrolessplating). Thus, typically iron deposition is conducted by a processcomprising contacting the support with a deposition bath comprising asource of the first metal in the absence of an externally appliedvoltage. For example, iron may be deposited via electroless depositionusing methods generally known in the art including, for example, thosedescribed in U.S. Pat. No. 6,417,133 and by Wan et al. in InternationalPublication No. WO 2006/031938. In various embodiments, as detailedbelow, the deposition bath comprises a reducing agent that reduces ionsof the first metal that are deposited at the surface of the support.

(a) Sources of Iron

Suitable sources of iron include iron salts such as the nitrate,sulfate, chloride, acetate, oxalate, and formate salts, and combinationsthereof. In various preferred embodiments, the source of iron comprisesiron chloride (i.e., FeCl₃), iron sulfate (i.e., Fe₂(SO₄)₃), or acombination thereof.

The concentration of iron source in the deposition bath is not narrowlycritical and is generally selected in view of the desired metal contentand/or the composition of the source. Often, the source of iron ispresent in the deposition bath at a concentration of at least about 5g/L and more typically from about 5 to about 20 g/L. In variousembodiments, the entire proportion of the source of iron is introducedinto the deposition bath prior to, during, or after addition of thecarbon support to the deposition bath and/or the vessel containingdeposition bath. Additionally or alternatively (including as describedin the working Examples), the source of iron may be metered, or pumpedinto the deposition bath and/or a vessel containing the carbon support.In this regard it is to be understood that metered addition of thesource of iron is controlled to provide deposition of a suitableproportion of iron at the support surface, regardless of theconcentration of iron source in the deposition bath at any point(s)during iron deposition.

(b) Iron Loading in Deposition Bath

As with other first metals (e.g., copper as described above), ironloading in the deposition bath may affect the quality and/or dispersionof iron deposition over a sufficient portion of the support surface. Theconcentration of iron in the deposition bath is generally controlled toaddress these concerns and others (e.g., agglomeration of first metal).For example, typically iron is present in the first metal depositionbath at a concentration of at least about 2 g/L, more typically at leastabout 3 g/L and, still more typically, at least about 4 g/L. Preferably,iron is present in the deposition bath at a concentration of from about2 to about 8 g/L, more preferably from about 3 to about 6 g/L and, stillmore preferably, from about 4 to about 5 g/L.

(c) Reducing Agents

To provide a driving force for deposition of a second metal thereon,preferably iron is deposited in an at least partially reduced state,e.g., as Fe⁺² and/or its fully reduced state as Fe⁰. Thus, in variousembodiments, the iron first metal deposition bath comprises a reducingagent. Any reducing agent is generally utilized under the conditions setforth above regarding copper deposition (e.g., concentration of reducingagent, etc.). Suitable reducing agents include sodium hypophosphite(NaH₂PO₂), formaldehyde (CH₂O), formic acid (HCOOH), salts of formicacid, sodium borohydride (NaBH₄), sodium triacetoxyborohydride(Na(CH₃CO₂)₃BH)), sodium alkoxides, hydrazine (H₂NNH₂), and ethyleneglycol. In view of the greater electropositivity of iron as compared tocopper, stronger reducing agents for iron first metal deposition may bepreferred as compared to those preferred for copper first metaldeposition. Thus, in various preferred embodiments the reducing agent issodium borohydride or ethylene glycol.

In those embodiments in which the reducing agent is sodium borohydrideand/or ethylene glycol, the molar ratio of reducing agent to irondeposited is generally at least 1, typically at least about 2, and moretypically at least about 3. Typically in accordance with theseembodiments, the molar ratio of sodium borohydride to iron deposited isform about 1 to about 5 and, more typically, from about 2 to about 4.

(d) Temperature

As with copper deposition, the temperature of the deposition bathaffects iron nucleation and agglomeration. Generally, the temperature ofthe deposition bath is sufficient to provide suitable nucleation andagglomeration, but preferably not at a level that promotes first metalagglomeration to an undesired degree. Generally, iron deposition bathtemperatures ranging from about 5° C. to about 60° C. may be utilized toprovide suitable catalysts. Often, the temperature of the irondeposition bath is above ambient conditions in order to providesufficient nucleation and, more particularly, suitable dispersion offirst metal over the support surface. Thus, typically the temperature ofthe iron deposition bath is from about 25° C. to about 60° C. and, moretypically, from about 25° C. to about 45° C.

(e) Agitation

The iron first metal deposition bath is typically agitated to promotedispersion of iron over the surface of the support. As in copperdeposition, agitation may also promote diffusion of the reducing agentthroughout the support. Any agitation during first metal deposition isgenerally conducted in accordance with the above description regardingcopper deposition.

(f) Deposition pH

As with copper deposition, iron deposition generally proceeds morereadily as deposition pH increases. Thus, typically the iron depositionpH is at least about 8, at least about 9, or at least about 10. Also aswith iron deposition, the presence of a coordinating agent (e.g.,sucrose) is currently believed to retard iron precipitation at high pHand thereby promote sufficient dispersion of the metal over the surfaceof the support. As noted, formation of a coordination complex betweenthe first metal and a coordinating agent is generally enhanced at theabove-noted pH levels. But at certain pH levels, deposition bath pH maynegatively impact solvation or iron ions and first metal reduction anddeposition. Thus, in various preferred embodiments the pH of the irondeposition bath is from about 8 to about 13, or from about 9 to about12.

5. First Metal Deposition Atmosphere

Regardless of the precise conditions of first metal deposition and thedispersion of first metal deposited at the support surface, oxidation ofdeposited first metal may reduce the proportion of first metal exchangesites available for second metal deposition. Accordingly, in variouspreferred embodiments, the first metal is deposited onto the support inthe presence of a non-oxidizing environment (e.g., a nitrogenatmosphere). Additionally or alternatively, water and/or otherdeposition bath components are degassed to remove dissolved oxygen usingmethods known to those skilled in the art.

B. Second Metal

Conventional noble metal-containing catalysts are generally prepared bydepositing a noble metal at the surface of a support, typically a porouscarbon support. Agglomeration of noble metal into particles, therebyreducing exposed metal catalytic surface area, has been observed withthese methods. In particular, an abundance of relatively largemetal-containing particles may represent inefficient usage of the metalby virtue of these particles providing a relatively low exposedcatalytic surface area per unit metal.

In accordance with various embodiments of the present invention, noblemetal-containing catalysts are prepared by a method in which the noblemetal is deposited in a manner that increases the exposed metalcatalytic surface area per unit weight of metal. More particularly, thenoble metal is deposited at the surface of one or more regions of firstmetal by displacement of first metal from the regions. It is currentlybelieved that deposition of the noble metal utilizing a first,sacrificial metal results in reduced noble metal agglomeration. Forexample, as noted elsewhere herein, deposition of the noble metal inthis manner provides a catalyst precursor structure in which the noblemetal deposited at the surface of one or more regions of a first metalis less prone to agglomeration than noble metal deposited directly ontothe surface of a porous support. It is further currently believed that,upon heat treatment of supports having thereon noble metal deposited inthis manner, metal particles are formed that provide improved noble(second) metal utilization (e.g., greater exposed metal catalyticsurface area per unit metal weight).

Generally, the second metal is deposited onto a first metal-impregnatedsupport by contact of the metal-impregnated support and a second metaldeposition bath. More particularly, the second metal is generallydeposited via electroless deposition in which the firstmetal-impregnated support and second metal deposition bath are contactedin the absence of an externally applied voltage.

As noted, in various embodiments, the second metal is a noble metal.Typically, the noble metal is selected from the group consisting ofplatinum, palladium, ruthenium, rhodium, iridium, silver, osmium, gold,and combinations thereof. In various preferred embodiments, the noblemetal comprises platinum. In still other preferred embodiments, thenoble metal comprises more than one metal (e.g., platinum and palladiumor platinum and gold).

The following discussion focuses on deposition of platinum as the secondmetal, but it is to be understood that the present invention likewisecontemplates utilizing any or all of the above-noted noble metals as thesecond metal. In addition, suitability of a combination of metals foruse in displacement deposition of a second metal onto one or moreregions of a first metal generally depends on their relativeelectropositivities. Thus, the present invention is not limited todeposition of noble metals as the second metal. For example, two metalsdesignated as candidate first metals elsewhere herein may provide thefirst and second metals so long as their relative electropositivitiesallow displacement deposition of the second metal onto one or moreregions of the first metal.

Suitable sources of platinum include those generally known in the artfor use in liquid phase deposition of platinum and include, for example,H₂PtCl₄, H₂PtCl₆, K₂PtCl₄, Na₂PtCl₆, and combinations thereof. Thus, invarious embodiments, the second metal deposition bath comprises a sourceof platinum including a platinum salt comprising platinum at anoxidation state of +2 and/or +4. As noted, in various preferredembodiments, the source of platinum provides platinum ions exhibiting anoxidation state of +2. However, it is to be understood that effectivecatalysts may be prepared utilizing sources of platinum that provideplatinum ions having other oxidation states (e.g., +4), and sources ofplatinum that provide platinum ions that comprise platinum ionsexhibiting oxidation states other than +2. Similarly, sources of noblemetals other than platinum and second metal sources generally thatprovide metal ions at lower oxidation states are likewise preferred. Forexample, it is currently believed that palladium provided by Na₂PdCl₄and PdCl₂ may be utilized to prepare active catalyst comprisingpalladium as the second metal.

Generally, the source of platinum is present in the second metaldeposition bath in a proportion that provides a molar concentration ofsecond metal ions less than the concentration of first metal ions in thefirst metal deposition bath. Typically, the molar ratio of copper ionsin the first metal deposition bath to noble metal ions in the secondmetal deposition bath is greater than 1, more typically at least about 2and, even more typically at least about 3 (e.g., at least about 5). Invarious preferred embodiments, the molar ratio of copper ions in thefirst metal deposition bath to noble metal ions in the second noblemetal deposition bath is typically greater than 1 to about 20, moretypically from about 2 to about 15, still more typically from about 3 toabout 10 and, even more typically, from about 5 to about 7.5.

Generally, the first metal-impregnated support is not subjected toelevated temperatures prior to contact with the second metal depositionbath. That is, the catalyst precursor structure is preferably notsubjected to temperatures that would promote formation ofmetal-containing particles (e.g., through agglomeration of first metalparticles). For example, the first and second metal-impregnated supportis generally subjected to temperatures of no more than about 200° C., nomore than about 150° C., and preferably no more than about 120° C. priorto contact with the second metal deposition bath.

Typically, the metal-impregnated support and second metal depositionbath are contacted at a temperature of at least about 5° C., typicallyat least about 10° C. and, more typically, at least about 15° C.Preferably, the first metal-impregnated support and the second metaldeposition bath are contacted at a temperature of from about 10° C. toabout 60° C., from about 20° C. to about 50° C., or from about 25° C. toabout 45° C.

Often, the second metal deposition bath has a pH less than the pH of thefirst metal deposition bath and is from about 1 to about 12 or fromabout 1.5 to about 10. In accordance with various embodiments, the pH ofthe deposition bath is from about 2 to about 7 or from about 3 to about5. Such pH conditions have been observed to be suitable for depositionof a noble (second) metal onto one or more regions of copper firstmetal. In various preferred embodiments, the first metal is iron. Ascompared to copper, iron may be more readily leached from the surface ofthe support as the pH of the deposition bath decreases. Thus, inaccordance with those embodiments in which the first metal is iron, thepH of the noble (second) metal deposition bath is typically from about 4to about 9, and preferably from about 5 to about 8 (e.g., about 7).

As noted above, preferably the first metal is deposited in anenvironment that avoids oxidation of deposited first metal that mayreduce the proportion of first metal exchange sites available for secondmetal deposition. Likewise, in various preferred embodiments, the secondmetal is also deposited onto the first metal-impregnated support in anon-oxidizing environment (e.g., a nitrogen atmosphere) to avoidoxidation of deposited first and second metal.

C. First and Second Metal-Impregnated Support

As noted, preferably the first metal deposited at the support surfaceprovides suitable exchange sites for deposition of second metal at thesurface of one or more regions of first metal and, more particularly, anexcess of exchange sites for second metal deposition. Accordingly,typically the atom ratio of first metal to second metal of the first andsecond metal-impregnated support (i.e., catalyst precursor structure) isat least about 1.5, more typically at least about 2 and, still moretypically, at least about 3 (e.g., at least about 4 or at least about5). Preferably, the atom ratio of first metal to second metal of thefirst and second metal-impregnated support is from about 1.5 to about 15more preferably from about 2 to about 15, still more preferably fromabout 3 to about 10 and, even more preferably, from about 4 to about 8.

As noted, heat treatment of the impregnated support provides first andnoble (second) metal-containing particles at the support surfaceincluding the noble (second) metal in a form that provides advantageousmetal utilization. An excess of first metal atoms to second metal atomson the impregnated support is believed to result in formation of suchparticles. For example, the excess of first metal to second metal atomson the impregnated support provides first metal-rich particles thatinclude a relatively low proportion of unexposed noble (second) metalthroughout the particles (e.g., a bimetallic alloy having an excess offirst metal atoms).

Additionally or alternatively, and as generally depicted in FIG. 2, heattreatment of the first and second metal-impregnated support may formmetal particles comprising a core and a shell at least partiallysurrounding the core. It is currently believed that the composition ofthe core and shell indicate improvements in metal utilization and, moreparticularly, improvements in second metal (e.g., noble metal)utilization. For example, the core of these particles is generally firstmetal-rich, thereby providing a relatively low proportion of unexposedsecond metal throughout the particles.

As the atom ratio of first metal to second metal in the catalystprecursor increases, the extent to which the first metal-rich core issurrounded by a second metal-containing shell may decrease. For example,a relatively high excess of first metal exchange sites for second metaldeposition may result in a portion of exchange sites that do notparticipate in displacement deposition of noble (second) metal. Suchparticles may be prepared from catalyst precursors in which the atomratio is near or above the above-noted upper limit of first metal tosecond metal atom ratios (e.g., about 10 or higher). Although lesspreferred, it should be understood that a decrease in the degree towhich the core is surrounded by a second metal-containing shell does notnecessarily indicate a lack of improved second metal utilization. Theseparticles may nonetheless provide improved metal utilization based on,for example, a first metal-rich core that provides a relatively lowproportion of unexposed, and potentially unutilized noble (second)metal. However, it is currently believed that the structure of theparticles may shift toward increased coverage of the first metal-richcore by the second metal-containing shell. More particularly, this shiftin form of the particles may comprise leaching of first metal from themetal particle at the support surface during use of the catalyst inliquid phase reactions. Second metal may likewise be removed or leachedfrom the particles, but it is currently believed that first metal isremoved from the particles to a greater degree than second metal.Accordingly, the atom ratio of first metal to second metal approachesmore preferred ranges and it is currently believed that as a result ofthis removal the structure of particles shifts to more preferred (i.e.,more extensive) coverage of the first metal-rich core by the secondmetal-containing shell. After a period of use, the leaching of firstmetal from the metal particles on the support surface generallydecreases. Following such a period of use, it is currently believed thatcatalysts comprising particles having a more preferred ratio of firstmetal to second metal atoms with the attendant shift in structure,thereafter exhibit performance characteristics comparable to catalystsprepared using the more preferred ratios of first metal to second metalatoms. This “self-correcting” behavior has been observed, for example,in connection with catalysts in which the first metal is copper and thesecond metal is platinum.

D. Heat Treatment of First and Second Metal-Impregnated Supports

As noted, it is to be understood that the metal-impregnated support ofthe present invention is a suitable catalyst as described in the workingexamples detailed herein. However, typically in accordance with variouspreferred embodiments, the metal-impregnated support is treated atelevated temperatures generally as detailed elsewhere herein (e.g., inthe presence of a non-oxidizing environment at temperatures in excess ofabout 800° C.) to form a finished catalyst. Typically, themetal-impregnated support is heated to temperatures from about 400° C.to about 1000° C., more typically from about 500° C. to about 950° C.,still more typically from about 600° C. to about 950° C. and, even moretypically, from about 700° C. to about 900° C. Subjectingmetal-impregnated supports to such temperatures provides finishedcatalysts exhibiting reduced metal leaching and improved metalutilization as detailed elsewhere herein (e.g., catalysts comprisingfirst metal-rich particles and/or particles including a first metal-richcore at least partially surrounded by a second metal-rich shell).

Stable metal particles (i.e., resistant to leaching) are currentlybelieved to be readily formed in the case of first and secondmetal-impregnated supports in which the first metal is iron and thesecond metal is platinum. Iron and platinum-impregnated supports (i.e.,iron-platinum catalyst precursors) have been observed to exhibitsuitable stability during reaction testing. Preferably, however, theiron-platinum catalyst precursor is subjected to elevated temperaturesto prepare a finished catalyst. It is currently believed that heatingthe iron-platinum impregnated support improves activity. But, in view ofthe advantageous stability of the iron and platinum-impregnatedsupports, suitable catalysts may be prepared therefrom by heating thecatalyst precursor to temperatures within, but at or near the lowerlimits of the above-noted ranges. Thus, in accordance with certainembodiments, platinum-iron impregnated supports are subjected to amaximum temperature of from about 400° C. to about 750° C., or fromabout 500° C. to about 650° C. to prepare a finished catalyst.

As noted, the degree of first and second metal alloying generallyincreases with increasing temperature to which the metal-impregnatedsupport is subjected. Accordingly, subjecting theiron/platinum-impregnated support to a relatively low maximumtemperature is currently believed to provide a relatively low degree ofiron and platinum alloying. Although catalysts of the present inventioninclude the first and second metals in a form that represents efficientmetal utilization (e.g., a first metal-rich alloy), alloy formationunavoidably results in unexposed noble (second) metal. Thus, preparingiron and platinum-containing catalysts by subjecting themetal-impregnated support to relatively low temperature may contributeto improved metal utilization. However, in this regard it is to be notedthat preparing iron and platinum-containing catalysts by subjecting thesupports to higher temperatures, e.g., in the ranges noted above such as700° C. or higher, is likewise currently believed to provide catalyststhat represent more efficient metal utilization.

E. Iron and Platinum Deposition Protocols

Suitable iron and platinum-containing catalysts generally may beprepared in accordance with the above discussion regarding iron (firstmetal) and platinum (second metal) deposition, both in accordance withthe above discussions concerning first and second metals generally, andspecifically iron and platinum. However, in accordance with the presentinvention it has been discovered that advantageous catalysts areprovided by combinations of particular features of iron (first metal)and platinum (second metal) deposition.

For example, in various preferred embodiments, the iron (first metal)deposition bath comprises ethylene glycol as a reducing agent, but doesnot comprise a separate coordinating agent (e.g., sucrose). However, itis to be understood that the ethylene glycol reducing agent may, infact, function as a coordinating agent to a certain degree.

In still other preferred embodiments, the iron deposition bath comprisesboth a reducing agent and a coordinating agent. In various suchembodiments, ethylene glycol is the reducing agent and sucrose is thecoordinating agent. In further such embodiments, ethylene glycol andsodium borohydride are utilized as reducing agents for iron deposition,and the iron deposition bath also comprises sucrose as a coordinatingagent.

In various other preferred embodiments, the iron (first metal)deposition bath comprises sodium borohydride as a reducing agentgenerally in accordance with the above discussion. The iron depositionbath does not comprise a separate coordinating agent (e.g., sucrose).

F. First and Second Metal-Containing Catalysts

As noted, first and noble (second) metal-impregnated supports typicallycontain an excess of first metal atoms over second metal atoms. Inaccordance with these and various other embodiments, generally the firstmetal constitutes at least about 1% by weight, at least about 1.5% byweight, or at least about 2% by weight of the catalyst. Typically thefirst metal constitutes at least about 3% by weight, at least about 4%by weight, or at least about 5% by weight of the catalyst. For example,preferably the first metal constitutes from about 3% to about 25% byweight of the catalyst, more preferably from about 4% to about 20% byweight of the catalyst and, still more preferably, from about 5% toabout 15% by weight of the catalyst. In various other embodiments (e.g.,those in which iron is the first metal), the first metal constitutesfrom about 1% to about 10% by weight, more preferably from about 1.5% toabout 8% by weight and, still more preferably, from about 2% to about 5%(e.g., about 4%) by weight of the catalyst.

In accordance with the foregoing, catalysts of various embodiments ofthe present invention generally contain at least about 1% by weightnoble (second) metal, at least about 2% by weight noble metal, or atleast about 3% by weight noble metal. Typically, the catalysts containless than about 8% by weight noble metal, more typically less than about7% by weight noble metal and, still more typically, less than about 6%by weight noble metal. In accordance with various preferred embodiments,the catalysts contain less than about 5% or less than about 4% by weightnoble metal (e.g., from about 1% to about 3% by weight noble metal).Catalysts prepared as detailed herein more efficiently utilize the noble(second) metal as compared to conventional catalysts, thereby providingcatalysts at least as active or even more active than conventional noblemetal-containing catalysts. For example, catalysts can be prepared thatinclude metal loadings similar to conventional noble metal-containingcatalysts, but are generally more active and, in various preferredembodiments, much more active than conventional noble metal-containingcatalysts. In this manner, catalytic activity can be increased withoutan increase in noble metal loading, which may be undesired due toprocessing limitations. In various embodiments, active catalysts can beprepared that contain from about 3% to about 6% by weight noble metal,or from about 4% to about 5% by weight noble metal.

By way of further example, more efficient metal usage by catalysts ofthe present invention allows preparation of catalysts that include areduced proportion of second metal as compared to conventional noblemetal-containing catalysts, but that are at least as active and, invarious preferred embodiments, more active than conventional noblemetal-containing catalysts. In this manner, catalysts of the presentinvention can provide activities equivalent to those provided byconventional noble metal-containing catalysts at lower noble metalloadings, or greater catalytic activities at equivalent noble metalloadings. For example, in various embodiments, active catalysts may beprepared that contain from about 1% to about 5% by weight, from about1.5% to about 4% by weight, or from about 2% to about 3% by weight noblemetal.

In various embodiments, first metal to second metal atom ratio in metalparticles at the surface of the catalyst support generally increaseswith increasing particle size. It is currently believed that as particlesize increases the portion of the particle constituting the firstmetal-rich core increases, while the portion (i.e., weight fraction) ofthe particles constituting the second metal-containing shell decreases.As previously noted, larger metal-containing particles are generallymore resistant to leaching from the surface of the catalyst support.However, a significant fraction of larger particles is generallyundesired in conventional noble metal-containing catalysts because asparticle size increases the proportion of noble metal distributed withinthe particle that does not contribute to effective catalytic surfacearea increases. Thus, a relatively high proportion of large particlescomprising a second metal-rich shell in accordance with the presentinvention provides improved stability, without the sacrifice in exposednoble (second) metal catalytic surface area associated with relativelylarge particles in conventional noble metal-containing catalysts.

For example, in various embodiments, the catalyst includesmetal-containing particles characterized by a particle size, asdetermined using electron microscopy, such that a significant fraction(e.g., at least about 80%, at least about 90%, or at least about 95%,number basis) of the particles are from about 5 to about 60 nm, or fromabout 5 to about 40 nm in their largest dimension. In addition, thethickness of the second metal-containing shells of the particles withinthese size distributions nm is typically less than about 3 nm, moretypically less than about 2 nm, and preferably less than about 1 nm(e.g., less than about 0.8 nm or less than about 0.6 nm).

Improvements in metal utilization may be characterized by an increase inthe proportion of exposed noble (second) metal of the catalyst. Moreparticularly, improvements in metal utilization may be indicated by anincrease in the surface area of exposed noble metal per unit weightcatalyst per unit weight noble metal. The total exposed noble metalsurface area of catalysts of the present invention may be determinedusing static carbon monoxide chemisorption analysis, including ProtocolA described in Example 67. The carbon monoxide chemisorption analysisdescribed in Example 67 includes first and second cycles. Catalysts ofthe present invention subjected to such analysis are generallycharacterized as chemisorbing at least about 500 μmoles of carbonmonoxide per gram catalyst per gram noble metal and, more generally, atleast about 600 μmoles of carbon monoxide per gram catalyst per gramnoble metal. Typically, catalysts of the present invention arecharacterized as chemisorbing at least about 700, at least about 800, atleast about 900, at least about 975, at least about 1000, or at leastabout 1100 μmoles of carbon monoxide per gram catalyst per gram noblemetal.

An alternative or additional indicator of efficient metal utilization isthe proportion of the noble (second) metal of the catalyst that may befound within a shell at least partially surrounding a first metal-richcore. Generally, at least about 10%, at least about 20%, at least about30%, at least about 40%, or at least about 50% of the noble metal ispresent within the shell of the metal particles. Typically, at leastabout 60% and, more typically, at least about 70% (e.g., at least about80% or at least about 90%) of the noble metal is present within theshell of the metal particles.

Additionally or alternatively, efficient metal utilization may beindicated by the proportion of noble (second) metal at the surface ofmetal particles. That is, efficient metal utilization may be indicatedby the proportion of noble metal at the surface of first metal-richparticles, e.g., second metal present in an alloy and/or within a secondmetal-rich shell at least partially surrounding a first metal-rich core.Generally, the atom percent of noble metal at the surface of first andnoble (second) metal-containing particles is at least about 2%, or atleast about 5%. Typically, the atom percent of noble metal at thesurface of first and noble metal-containing particles is at least about10%, more typically at least about 20%, even more typically at leastabout 30%, and preferably at least about 40% (e.g., at least about 50%).

Energy dispersive x-ray spectroscopy (EDX) line scan analysis resultsfor catalysts of the present invention (e.g., as described in Protocol Bin Example 68) also indicate efficient metal utilization. Moreparticularly, line scan analysis results for metal particles ofcatalysts of the present invention indicate a distribution of noble(second) metal in which a significant fraction of the noble (second)metal is present within a shell at least partially surrounding a firstmetal-rich core. Additionally or alternatively, line scan analysisresults for metal particles of catalysts of the present inventionindicate a noble metal distribution in which a significant fraction ofthe noble metal is disposed at or near the surface of a metalparticle(s).

Efficient metal utilization in particles of catalysts of the presentinvention is indicated by a second metal distribution that produces anEDX line scan signal that does not vary significantly over a scanningregion. As used herein, the term scanning region refers to the portionof the largest dimension of the particle analyzed over which arelatively low degree of variation in second metal signal indicatesimproved metal utilization. A relatively constant second metal line scansignal over a scanning region corresponding to a significant portion ofthe largest dimension of the particle indicates that a significantfraction of the second metal is distributed near the surface of theparticle rather than throughout the metal particle. By contrast, thelatter type of distribution would cause the second metal signal toincrease (decrease) significantly in that portion of the scanning regionwhere the probe is directed to a thicker (thinner) dimension of theparticle. For example, in various embodiments, the second metal signalgenerated during EDX line scan analysis of a particle at the surface ofa catalyst in accordance with the present invention varies by no morethan about 25%, no more than about 20%, no more than about 15%, no morethan about 10%, or no more than about 5% across a scanning region thatis a least about 70% of the largest dimension of at least one particle.In further embodiments, the second metal signal varies by no more thanabout 20%, no more than about 15%, no more than about 10%, or no morethan about 5% across a scanning region that is at least about 60% of thelargest dimension of at least one particle. In still furtherembodiments, the second metal signal varies by no more than about 15%,no more than about 10%, or no more than about 5% across a scanningregion that is at least about 50% of the largest dimension of at leastone particle.

The particles having metal distributions characterized by EDX line scananalysis as detailed above are typically first metal-rich and, moreparticularly, typically include the second metal and first metal at anatomic ratio of second metal to first metal in a particle(s) analyzed ofless than 1:1. Typically, the second metal to first metal atomic ratioof the particle(s) is less than about 0.8:1 and, more typically, lessthan about 0.6:1 (e.g., less than about 0.5:1).

Generally, the first and second metal particle(s) of catalysts of thepresent invention having a second metal distribution characterized byEDX line scan analysis indicating efficient metal utilization have alargest dimension of at least about 6 nm, typically at least about 8 nm,more typically at least about 10 nm and, still more typically, at leastabout 12 nm.

The relative magnitudes of first and second metal signals across thescanning region may also indicate first and second metal distributionsin a form that indicates efficient metal utilization. More particularly,generally in accordance with various embodiments, the ratio of themaximum first metal signal to the maximum second metal signal across thescanning region is at least about 1.5:1, at least about 2:1, or at leastabout 2.5:1. Typically, the ratio of the maximum first metal signal tothe maximum second metal signal across the scanning region is at leastabout 3:1, at least about 4:1, or at least about 5:1.

It is to be understood that efficient metal utilization may be indicatedby identification of at least one particle at the surface of thecatalyst support having a noble (second) metal distributioncharacterized as described above. That is, the population of metalparticles at the surface of the catalyst support may include bothparticles satisfying one or more of the noble metal distributioncharacteristics and those that do not. However, metal utilization isenhanced as the proportion of metal particles exhibiting these preferrednoble metal distribution characteristics increases and typically aplurality of metal particles will possess these characteristics. Moretypically, the second metal distribution of each of a portion (numberbasis) of the particles at the surface of the support indicatesefficient metal utilization. Generally, at least about 1%, at leastabout 5%, at least about 10%, at least about 15%, at least about 20%, orat least about 25% of the metal particles satisfy the second metaldistribution characteristics. Typically, at least about 30%, at leastabout 35%, at least about 40%, at least about 45%, at least about 50%,at least about 55%, at least about 60%, or at least about 65% of themetal particles satisfy the second metal distribution characteristics.The proportion of metal particles satisfying one or more of the noblemetal distribution characteristics is somewhat dependent upon theparticular first metal and second metal combination. For example,catalysts prepared with copper and platinum as the first and secondmetals, respectively, have been observed to produce catalysts in which alarge portion of metal particles at the surface thereof possess thesepreferred noble metal distribution characteristics. Accordingly, inthese and other preferred embodiments, at least about 70%, at leastabout 75%, at least about 85%, or at least about 90% of the metalparticles at the surface of the support satisfy one or more of thesecond metal distribution characteristics determined by EDX line scananalysis.

As previously noted, in various embodiments of the present invention(e.g., in which copper is the first metal and platinum is the secondmetal) the second metal-rich shell may provide relatively low coverageof the first metal-rich core and, during subsequent use of the catalyst,the structure of the particles may shift toward increased coverage ofthe first metal-rich core by the second metal-containing shell. Thisshift generally comprises leaching of the first metal from the metalparticles at the support surface. Second metal may be removed or leachedfrom the particles, but to a lesser degree than first metal is removedfrom the particles. This behavior has been observed to provide a shifttoward preferred first metal to second metal atomic ratios.

Platinum-iron catalysts of the present invention have been observed tobehave as described. That is, during use, iron and platinum may beleached from the metal particles at the surface of the catalyst and,more particularly, iron is leached from the particles to a greaterdegree than platinum. Leaching in this manner may proceed in accordancewith the “self-correcting” mechanism described above in connection withplatinum-copper catalysts. However, leaching may also proceed to formplatinum-iron particles of advantageous structures. Rather thancompensating for a relatively low excess of first metal to second metalto provide a structure in which the atomic ratio of first metal tosecond metal is at a suitable excess, leaching of first metalpredominates over any leaching of second metal to such a degree that oneor more particles are provided that exhibit minimal, if any, excess offirst metal to second metal. In fact, in various embodiments, a catalyststructure exhibiting an excess of second metal to first metal isachieved. Although these particles may not include a first metal-richalloy or a first metal-rich core at least partially surrounded by asecond metal-rich shell, they do nonetheless provide improved metalutilization.

In various such embodiments, the metal particles at the surface of thecatalyst are in the form of a structure comprising a discontinuous shellcomprising a layer of first metal atoms and a layer (e.g., monolayer) ofsecond metal atoms at the surface of the first metal atoms. Reference toa shell in connection with these embodiments does not indicate thepresence of a continuous or discontinuous shell surrounding a relativelycontinuous core. Rather, shell refers to the overall structure of theresulting particle. The shell structure may surround an inner regionincluding first metal, but the inner regions of the shell structure arenot in the form of a relatively continuous first metal-rich coresurrounded by the outer regions of the shell structure. Thediscontinuous porous shell generally comprises pores and, moreparticularly, nanopores (i.e., pores having a size in their largestdimension of from about 1 to about 6 nanometers (nm), or from about 2 toabout 5 nm). In this manner, the shell structure may be referred to as adiscontinuous nanoporous shell. In accordance with such embodiments, theatomic ratio of iron (first metal) to platinum (second metal) isgenerally less than 1:1, typically from about 0.25:1 to about 0.9:1,more typically from about 0.4:1 to about 0.75:1 and, more typically,from about 0.4:1 to about 0.6:1 (e.g., about 0.5:1). Further inaccordance with these embodiments, the layer or regions of first metalgenerally have a thickness of no more than about 5 first metal atoms,typically no more than about 3 first metal atoms and, still moretypically, no more than about 2 first metal atoms. Additionally oralternatively, the layer or regions of second metal atoms generally havea thickness of no more than about 5 second metal atoms, typically nomore than about 4 second metal atoms, more typically no more than about3 second metal atoms and, more typically, no more than about 2 secondmetal atoms.

Extensive leaching of metal from catalyst particles to formplatinum-iron “shell” particles has been observed to occur during useunder certain conditions (e.g., acidic conditions prevailing duringoxidation of PMIDA). Experimental evidence indicates that catalystsincluding platinum-iron shell particles are effective for use in, forexample, the liquid phase oxidation of PMIDA. Thus, rather than simplyrelying on formation of the shell structure during use, catalystsincluding platinum-iron shell particles may be prepared by a processgenerally as described above for preparation of platinum-iron catalystsfurther including treatment for leaching of metals from one or moreparticles of the catalyst prior to or during use of the catalyst.Generally, treatment for metal leaching to form platinum-iron shellparticles comprises contacting a platinum-iron catalyst with a suitableliquid medium. Typically, the liquid medium is acidic and the catalystis contacted with the liquid medium at a temperature of at least about5° C., or at least about 15° C.

III. Use of Oxidation Catalysts

Oxidation catalysts of the present invention may be used for liquidphase oxidation reactions. Examples of such reactions include theoxidation of alcohols and polyols to form aldehydes, ketones, and acids(e.g., the oxidation of 2-propanol to form acetone, and the oxidation ofglycerol to form glyceraldehyde, dihydroxyacetone, or glyceric acid);the oxidation of aldehydes to form acids (e.g., the oxidation offormaldehyde to form formic acid, and the oxidation of furfural to form2-furan carboxylic acid); the oxidation of tertiary amines to formsecondary amines (e.g., the oxidation of nitrilotriacetic acid (NTA) toform iminodiacetic acid (IDA)); the oxidation of secondary amines toform primary amines (e.g., the oxidation of IDA to form glycine); andthe oxidation of various acids (e.g., formic acid or acetic acid) toform carbon dioxide and water.

The above-described catalysts are especially useful in liquid phaseoxidation reactions at pH levels less than 7, and in particular, at pHlevels less than 3. One such reaction is the oxidation of PMIDA or asalt thereof to form an N-(phosphonomethyl)glycine product in anenvironment having pH levels in the range of from about 1 to about 2.This reaction is often carried out in the presence of solvents whichsolubilize noble metals and, in addition, the reactants, intermediates,or products often solubilize noble metals.

The oxidation catalyst disclosed herein is particularly suited forcatalyzing the liquid phase oxidation of a tertiary amine to a secondaryamine, for example in the preparation of glyphosate and relatedcompounds and derivatives. For example, the tertiary amine substrate maycorrespond to a compound of Formula I having the structure

wherein R¹ is selected from the group consisting of R⁵OC(O)CH₂— andR⁵OCH₂CH₂—, R² is selected from the group consisting of R⁵OC(O)CH₂—,R⁵OCH₂CH₂—, hydrocarbyl, substituted hydrocarbyl, acyl, —CHR⁶PO₃R⁷R⁸,and —CHR⁹SO₃R¹⁰, R⁶, R⁹ and R¹¹ are selected from the group consistingof hydrogen, alkyl, halogen and —NO₂, and R³, R⁴, R⁵, R⁷, R⁸ and areindependently selected from the group consisting of hydrogen,hydrocarbyl, substituted hydrocarbyl and a metal ion. Preferably, R¹comprises R⁵OC(O)CH₂—, R¹¹ is hydrogen, R⁵ is selected from hydrogen andan agronomically acceptable cation and R² is selected from the groupconsisting of R⁵OC(O)CH₂—, acyl, hydrocarbyl and substitutedhydrocarbyl.

As noted above, the oxidation catalyst of the present invention isparticularly suited for catalyzing the oxidative cleavage of a PMIDAsubstrate to form N-(phosphonomethyl)glycine product. In such anembodiment, the catalyst is effective for oxidation of by-productformaldehyde to formic acid, carbon dioxide and/or water. Moreparticularly, it is currently believed that catalysts of the presentinvention may provide improvements in activity for PMIDA, formaldehyde,and/or formic acid oxidation as compared to conventional noblemetal-containing catalysts, either generally or on a per unit metalweight basis.

As is recognized in the art, the liquid phase oxidation ofN-(phosphonomethyl)iminodiacetic acid substrates may be carried out in abatch, semi-batch or continuous reactor system containing one or moreoxidation reaction zones. The oxidation reaction zone(s) may be suitablyprovided by various reactor configurations, including those that haveback-mixed characteristics, in the liquid phase and optionally in thegas phase as well, and those that have plug flow characteristics.Suitable reactor configurations having back-mixed characteristicsinclude, for example, stirred tank reactors, ejector nozzle loopreactors (also known as venturi-loop reactors) and fluidized bedreactors. Suitable reactor configurations having plug flowcharacteristics include those having a packed or fixed catalyst bed(e.g., trickle bed reactors and packed bubble column reactors) andbubble slurry column reactors. Fluidized bed reactors may also beoperated in a manner exhibiting plug flow characteristics. Theconfiguration of the oxidation reactor system, including the number ofoxidation reaction zones and the oxidation reaction conditions are notcritical to the practice of the present invention. Suitable oxidationreactor systems and oxidation reaction conditions for liquid phasecatalytic oxidation of an N-(phosphonomethyl)iminodiacetic acidsubstrate are well-known in the art and described, for example, by Ebneret al., U.S. Pat. No. 6,417,133, by Leiber et al., U.S. Pat. No.6,586,621, and by Haupfear et al., U.S. Pat. No. 7,015,351, the entiredisclosures of which are incorporated herein by reference.

The description below discloses with particularity the use of catalystsdescribed above acting as the catalyst to effect the oxidative cleavageof a PMIDA substrate to form an N-(phosphonomethyl)glycine product. Itshould be recognized, however, that the principles disclosed below aregenerally applicable to other liquid phase oxidative reactions,especially those at pH levels less than 7 and those involving solvents,reactants, intermediates, or products which solubilize noble metals.

To begin the PMIDA oxidation reaction, it is preferable to charge thereactor with the PMIDA substrate, catalyst, and a solvent in thepresence of oxygen. The solvent is most preferably water, although othersolvents (e.g., glacial acetic acid) are suitable as well.

The reaction may be carried out in a wide variety of batch, semi-batch,and continuous reactor systems. The configuration of the reactor is notcritical. Suitable conventional reactor configurations include, forexample, stirred tank reactors, fixed bed reactors, trickle bedreactors, fluidized bed reactors, bubble flow reactors, plug flowreactors, and parallel flow reactors.

When conducted in a continuous reactor system, the residence time in thereaction zone can vary widely depending on the specific catalyst andconditions employed. Typically, the residence time can vary over therange of from about 3 to about 120 minutes. Preferably, the residencetime is from about 5 to about 90 minutes, and more preferably from about5 to about 60 minutes. When conducted in a batch reactor, the reactiontime typically varies over the range of from about 15 to about 120minutes. Preferably, the reaction time is from about 20 to about 90minutes, and more preferably from about 30 to about 60 minutes.

In a broad sense, the oxidation reaction may be practiced in accordancewith the present invention at a wide range of temperatures, and atpressures ranging from sub-atmospheric to super-atmospheric. Use of mildconditions (e.g., room temperature and atmospheric pressure) haveobvious commercial advantages in that less expensive equipment may beused. However, operating at higher temperatures and super-atmosphericpressures, while increasing capital requirements, tends to improve phasetransfer between the liquid and gas phase and increase the PMIDAoxidation reaction rate.

Preferably, the PMIDA oxidation reaction is conducted at a temperatureof from about 20 to about 180° C., more preferably from about 50 toabout 140° C., and most preferably from about 80 to about 110° C. Attemperatures greater than about 180° C., the raw materials tend to beginto slowly decompose.

The pressure used during the PMIDA oxidation generally depends on thetemperature used. Preferably, the pressure is sufficient to prevent thereaction mixture from boiling. If an oxygen-containing gas is used asthe oxygen source, the pressure also preferably is adequate to cause theoxygen to dissolve into the reaction mixture at a rate sufficient suchthat the PMIDA oxidation is not limited due to an inadequate oxygensupply. The pressure preferably is at least equal to atmosphericpressure. More preferably, the pressure is from about 30 to about 500psig, and most preferably from about 30 to about 130 psig.

The concentration of the catalyst prepared in accordance with thepresent invention in the reaction mixture is preferably is from about0.1 to about 10% by weight ([mass of catalyst÷total reactionmass]×100%). More preferably, the catalyst concentration preferably isfrom about 0.1 to about 5% by weight, still more preferably from about0.2 to about 5% by weight and, most preferably, from about 0.3 to about1.5% by weight. Concentrations greater than about 10% by weight aredifficult to filter. On the other hand, concentrations less than about0.1% by weight tend to produce unacceptably low reaction rates.

As noted, catalysts prepared in accordance with the methods of thepresent invention provide for efficient metal utilization. Thus,catalysts of the present invention may provide sufficient activity atlower catalyst loadings as compared to loadings associated withconventional noble metal-containing catalysts. Accordingly, catalystsloadings in accordance with the present invention may suitably be at ornear the lower limits of the above-noted ranges. However, it is to beunderstood that utilizing a lower catalyst loading is not a criticalaspect of the present invention. In fact, a further aspect of thepresent invention involves utilizing the catalysts of the presentinvention at loadings similar to those associated with conventionalnoble metal-containing catalysts while providing improved catalyticactivity based on the improvements in metal utilization.

The concentration of PMIDA substrate in the feed stream is not critical.Use of a saturated solution of PMIDA substrate in water is preferred,although for ease of operation, the process is also operable at lesseror greater PMIDA substrate concentrations in the feed stream. If thecatalyst is present in the reaction mixture in a finely divided form, itis preferred to use a concentration of reactants such that all reactantsand the N-(phosphonomethyl)glycine product remain in solution so thatthe catalyst can be recovered for re-use, for example, by filtration. Onthe other hand, greater concentrations tend to increase reactorthrough-put. Alternatively, if the catalyst is present as a stationaryphase through which the reaction medium and oxygen source are passed, itmay be possible to use greater concentrations of reactants such that aportion of the N-(phosphonomethyl)glycine product precipitates.

Normally, a PMIDA substrate concentration of up to about 50% by weight([mass of PMIDA substrate÷total reaction mass]×100%) may be used(especially at a reaction temperature of from about 20 to about 180°C.). Preferably, a PMIDA substrate concentration of up to about 25% byweight is used (particularly at a reaction temperature of from about 60to about 150° C.) More preferably, a PMIDA substrate concentration offrom about 12 to about 18% by weight is used (particularly at a reactiontemperature of from about 100 to about 130° C.). PMIDA substrateconcentrations below 12% by weight may be used, but are less economicalbecause a relatively low payload of N-(phosphonomethyl)glycine productis produced in each reactor cycle and more water must be removed andenergy used per unit of N-(phosphonomethyl)glycine product produced.Relatively low reaction temperatures (i.e., temperatures less than 100°C.) often tend to be less advantageous because the solubility of thePMIDA substrate and N-(phosphonomethyl)glycine product are bothrelatively low at such temperatures.

The oxygen source for the PMIDA oxidation reaction may be anyoxygen-containing gas or a liquid comprising dissolved oxygen.Preferably, the oxygen source is an oxygen-containing gas. As usedherein, an oxygen-containing gas is any gaseous mixture comprisingmolecular oxygen which optionally may comprise one or more diluentswhich are non-reactive with the oxygen or with the reactant or productunder the reaction conditions.

Examples of such gases are air, pure molecular oxygen, or molecularoxygen diluted with helium, argon, nitrogen, or other non-oxidizinggases. For economic reasons, the oxygen source most preferably is air,oxygen-enriched air, or pure molecular oxygen.

Oxygen may be introduced by any conventional means into the reactionmedium in a manner which maintains the dissolved oxygen concentration inthe reaction mixture at a desired level. If an oxygen-containing gas isused, it preferably is introduced into the reaction medium in a mannerwhich maximizes the contact of the gas with the reaction solution. Suchcontact may be obtained, for example, by dispersing the gas through adiffuser such as a porous frit or by stirring, shaking, or other methodsknown to those skilled in the art.

The oxygen feed rate preferably is such that the PMIDA oxidationreaction rate is not limited by oxygen supply. If the dissolved oxygenconcentration is too high, however, the catalyst surface tends to becomedetrimentally oxidized, which, in turn, tends to lead to more leachingof noble metal present in the catalyst and decreased formaldehydeactivity (which, in turn, leads to more NMG being produced). Generally,it is preferred to use an oxygen feed rate such that at least about 40%of the oxygen is utilized. More preferably, the oxygen feed rate is suchthat at least about 60% of the oxygen is utilized. Even more preferably,the oxygen feed rate is such that at least about 80% of the oxygen isutilized. Most preferably, the rate is such that at least about 90% ofthe oxygen is utilized. As used herein, the percentage of oxygenutilized equals: (the total oxygen consumption rate÷oxygen feedrate)×100%. The term “total oxygen consumption rate”means the sum of:(i) the oxygen consumption rate (“R_(i)”) of the oxidation reaction ofthe PMIDA substrate to form the N-(phosphonomethyl)glycine product andformaldehyde, (ii) the oxygen consumption rate (“R_(ii)”) of theoxidation reaction of formaldehyde to form formic acid, and (iii) theoxygen consumption rate (“R_(iii)”) of the oxidation reaction of formicacid to form carbon dioxide and water.

In various embodiments of this invention, oxygen is fed into the reactoras described above until the bulk of PMIDA substrate has been oxidized,and then a reduced oxygen feed rate is used. This reduced feed ratepreferably is used after about 75% of the PMIDA substrate has beenconsumed. More preferably, the reduced feed rate is used after about 80%of the PMIDA substrate has been consumed. Where oxygen is supplied aspure oxygen or oxygen-enriched air, a reduced feed rate may be achievedby purging the reactor with (non-enriched) air, preferably at avolumetric feed rate which is no greater than the volumetric rate atwhich the pure molecular oxygen or oxygen-enriched air was fed beforethe air purge. The reduced oxygen feed rate preferably is maintained forfrom about 2 to about 40 minutes, more preferably from about 5 to about20 minutes, and most preferably from about 5 to about 15 minutes. Whilethe oxygen is being fed at the reduced rate, the temperature preferablyis maintained at the same temperature or at a temperature less than thetemperature at which the reaction was conducted before the air purge.Likewise, the pressure is maintained at the same or at a pressure lessthan the pressure at which the reaction was conducted before the airpurge. Use of a reduced oxygen feed rate near the end of the PMIDAreaction allows the amount of residual formaldehyde present in thereaction solution to be reduced without producing detrimental amounts ofAMPA by oxidizing the N-(phosphonomethyl)glycine product.

Reduced losses of noble metal may be observed with this invention if asacrificial reducing agent is maintained or introduced into the reactionsolution. Suitable reducing agents include formaldehyde, formic acid,and acetaldehyde. Most preferably, formic acid, formaldehyde, ormixtures thereof are used. Experiments conducted in accordance with thisinvention indicate that if small amounts of formic acid, formaldehyde,or a combination thereof are added to the reaction solution, thecatalyst will preferentially effect the oxidation of the formic acid orformaldehyde before it effects the oxidation of the PMIDA substrate, andsubsequently will be more active in effecting the oxidation of formicacid and formaldehyde during the PMIDA oxidation. Preferably from about0.01 to about 5% by weight ([mass of formic acid, formaldehyde, or acombination thereof total reaction mass]×100%) of sacrificial reducingagent is added, more preferably from about 0.01 to about 3% by weight ofsacrificial reducing agent is added, and most preferably from about 0.01to about 1% by weight of sacrificial reducing agent is added.

In certain embodiments, unreacted formaldehyde and formic acid arerecycled back into the reaction mixture for use in subsequent cycles. Inthis instance, an aqueous recycle stream comprising formaldehyde and/orformic acid also may be used to solubilize the PMIDA substrate in thesubsequent cycles. Such a recycle stream may be generated by evaporationof water, formaldehyde, and formic acid from the oxidation reactionmixture in order to concentrate and/or crystallize productN-(phosphonomethyl)glycine. Overheads condensate containing formaldehydeand formic acid may be suitable for recycle.

Typically, the concentration of N-(phosphonomethyl)glycine in theproduct mixture may be as great as 40% by weight, or greater.Preferably, the N-(phosphonomethyl)glycine concentration is from about 5to about 40%, more preferably from about 8 to about 30%, and still morepreferably from about 9 to about 15%. Concentrations of formaldehyde inthe product mixture are typically less than about 0.5% by weight, morepreferably less than about 0.3%, and still more preferably less thanabout 0.15%.

Following the oxidation, the catalyst preferably is subsequentlyseparated by filtration. The N-(phosphonomethyl)glycine product may thenbe isolated by precipitation, for example, by evaporation of a portionof the water and cooling.

In certain embodiments, it should be recognized that the catalyst ofthis invention has the ability to be reused over several cycles,depending on how oxidized its surface becomes with use. Even after thecatalyst becomes heavily oxidized, it may be reused by beingreactivated. To reactivate a catalyst having a heavily oxidized surface,the surface preferably is first washed to remove the organics from thesurface. It then preferably is reduced in the same manner that acatalyst is reduced after the noble metal is deposited onto the surfaceof the support, as described above.

Noble metal-containing catalysts including a treated porous substrateprepared by the present method may also be used in combination with asupplemental promoter as described, for example, in U.S. Pat. Nos.6,586,621; 6,963,009, the entire contents of which are incorporatedherein by reference for all relevant purposes.

N-(phosphonomethyl)glycine product prepared in accordance with thepresent invention may be further processed in accordance with manywell-known methods in the art to produce agronomically acceptable saltsof N-(phosphonomethyl)glycine commonly used in herbicidal glyphosatecompositions. As used herein, an “agronomically acceptable salt” isdefined as a salt which contains a cation(s) that allows agriculturallyand economically useful herbicidal activity of anN-(phosphonomethyl)glycine anion. Such a cation may be, for example, analkali metal cation (e.g., a sodium or potassium ion), an ammonium ion,an isopropyl ammonium ion, a tetra-alkylammonium ion, a trialkylsulfonium ion, a protonated primary amine, a protonated secondary amine,or a protonated tertiary amine.

IV. Additional Embodiments

A. Pore Blocking

With regard to disposing or depositing a pore blocking compound withinsubstrate pores as detailed elsewhere herein, it is to be noted that thepresent invention is not limited to disposing or depositing a poreblocking compound within the smallest substrate pores (e.g.,micropores). That is, various embodiments of the present invention aredirected to disposing or depositing a pore blocker within pores of anintermediate or larger size range. In this manner, various embodimentsof the present invention provide further opportunities for controllingthe sizes of pores that are blocked (i.e., further opportunities forcontrolling, or tuning blocking of pores). For example, in addition tomicropores, porous carbon supports that may be treated by the presentmethod have pores of larger dimensions (e.g., pores having a largestdimension of from about 20 Å to about 3000 Å).

Disposing or depositing a pore blocking agent within pores of a sizeabove the micropore size range proceeds generally in accordance with theabove-described method. For example, the substrate may be contacted withthe pore blocking compound and/or one or more precursors. Further inaccordance with the above-described method, the pore blocker may beretained within the targeted pores by virtue of exhibiting at least onedimension larger than the openings of the targeted pores. And regardlessof whether the pore blocking agent is introduced into the targeted poresor formed in situ, the pore blocker may be retained within the targetedpores by virtue of a conformational arrangement of the pore blocker.

As noted above, when relatively small pores are targeted by the poreblocker, the pore blocker may enter the non-targeted pores andsubsequently exit therefrom (e.g., by virtue of contacting with a liquidwashing medium). It is to be noted that a pore blocker targetingintermediate and/or larger size may not enter the pores smaller than thetargeted pores. However, this does not impact the goal of blocking ofintermediate and/or larger sized pores.

It is currently believed that a variety of compounds are suitable aspore blocking compounds for the purpose of blocking pores above themicropore size range. For example, the pore blocker may be selected fromthe group consisting of various hydrophilic polymers (e.g., variouspolyethylene glycols), and combinations thereof.

In various embodiments, the intermediate and/or larger size pore blockermay comprise the product of a reaction between one or more pore blockingcompound precursors. For example, it has been observed that the couplingproduct of a ketone and a dihydric alcohol may be utilized as a poreblocker.

As with micropores as noted above, it is believed that the presence ofthe pore blocking compound within targeted pores outside the microporedomain will cause at least a portion of the “blocked” pores to appear asa non-porous portion of the substrate during surface area measurements,thereby reducing the proportion of surface area that would otherwise beprovided by the targeted pores if they were not blocked. This blockingof the targeted pores is currently believed to provide a reduction inthe surface area of the treated substrate provided by the targetedpores. For example, in various embodiments, the surface area of thetreated substrate provided by the pores outside (i.e., above) themicropore size range is generally no more than about 80% or no more thanabout 70% of the surface area of the substrate provided by these poresprior to treatment. Typically, the surface area of the treated substrateprovided by the targeted pores is no more than about 60% and moretypically no more than about 50% of the surface area of the substrateprovided by these pores prior to treatment.

B. Pore Blocking of Catalyst Pores

As noted, persistence of the pore blocker in treated substrates of thepresent invention is not critical to provide the advantages describedabove (e.g., a reduced proportion of metal crystallites at the surfaceof a porous carbon support among relatively small pores of the substratesurface). And it is currently believed that the pore blocker is mostlikely decomposed and/or otherwise removed from the substrate surfacebefore calcining. In various alternative embodiments, the methods fortreating porous substrates may be applied to treatment of finishedcatalysts. For example, catalysts comprising a noble metal depositedonto a carbon support may be treated by depositing a pore blocker at thesurface of the catalyst within its relatively small pores. It iscurrently believed that the presence of the pore blocker within therelatively small pores may promote preferential contact of reactantswith the deposited metal among the intermediate and larger-sized porousregions within which the deposited metal is more accessible to thereactants. In this manner, conversion of reactants to products may bepromoted by reducing the proportion of reactants that contact depositedmetal among the relatively small porous regions in which the depositedmetal may be relatively inaccessible to the reactants. By way of furtherexample, treating carbon-supported catalysts suitable for in preparationof DSIDA from DEA in accordance with the methods detailed are currentlybelieved to provide catalysts including a reduced proportion of exposednoble metal and, accordingly, reduced by-product (e.g., glycine and/oroxalate). However, it is to be understood that treatment of finishedcatalyst (i.e., carbon or metal-containing having one or more metalsdeposited thereon) is not a critical aspect of the invention and thatcatalysts prepared using substrates treated by the present methods haveproven to be effective catalysts.

C. Non-Carbon Supports

In addition to treatment of porous carbon supports as detailed herein,the method of the present invention for blocking certain pores of asubstrate may be used to treat non-carbonaceous supports. Moreparticularly, the methods detailed herein may be used for treatment ofporous metal alloys often referred to as metal sponges. Metal spongealloys that may be treated by the present method are described, forexample, in U.S. Pat. Nos. 5,627,125; 5,916,840; 6,376,708, and6,706,662, the entire contents of which are incorporated herein byreference for all relevant purposes. It is currently believed thattreated metal-containing substrates may exhibit one or more of theabove-noted properties concerning treated porous carbon substrates.

D. Preparation of Carboxylic Acids

In addition to PMIDA oxidation as detailed elsewhere herein, catalystsincluding treated substrates prepared by the present method arecurrently believed to be suitable for use in other reactions. Forexample, catalysts including treated substrates prepared by the presentmethod may be used in the preparation of carboxylic acids including, forexample, the preparation of disodiumiminodiacetic acid (DSIDA) bydehydrogenation of diethanolamine (DEA). More particularly, catalystsincluding treated substrates of the present invention may address one ormore issues that may be observed with conventional catalysts utilized inpreparation of carboxylic acids such as DSIDA. For example, suitablecatalysts often include copper deposited over the surface of a carbonsupport having a noble metal (e.g., platinum or palladium) at itssurface. It is currently believed that at least a portion, and possiblya significant fraction of the noble metal may remain exposed afterdeposition of the copper. Excessive exposed noble metal is undesiredsince it is believed to promote formation of various undesiredby-products (e.g., glycine and oxalate). A substantial portion, if notnearly all the exposed noble metal is believed to be at the surface ofthe support within relatively small pores that are inaccessible tocopper during its deposition. Other catalysts suitable for preparationof carboxylic acids include copper deposited at the surface ofmetal-containing (e.g., nickel-containing) sponges. As with exposednoble metal at the surface of carbon-supported catalysts, metal supportsurface that is not coated by the copper within relatively small poresof the metal sponge support are believed to contribute to formation ofundesired by-products. It is currently believed that selective blockingof relatively small pores of substrates in accordance with the methodsdetailed herein may be used to prepare effective carbon- andmetal-supported catalysts that may address one or more of theabove-noted issues.

Preparation of DSIDA from DEA using a catalyst comprising a substratetreated as detailed herein generally proceeds in accordance with methodsknown in the art including, for example, U.S. Pat. Nos. 5,627,125;5,916,840; 6,376,708, and U.S. Pat. No. 6,706,662, the entire contentsof which are incorporated herein by reference for all relevant purposes.

The present invention is illustrated by the following examples which aremerely for the purpose of illustration and not to be regarded aslimiting the scope of the invention or the manner in which it may bepracticed.

EXAMPLES

The following non-limiting examples are provided to further illustratethe present invention.

I. Pore Plugging

Example 1

Three carbon supports were treated to determine the effectiveness ofcandidate pore blocking compounds. Support A had a total Langmuirsurface area of approximately 1500 m²/g (including total microporesurface area of approximately 1279 m²/g and total macropore surface areaof approximately 231 m²/g). Support B had a total Langmuir surface areaof approximately 2700 m²/g (including total micropore surface area ofapproximately 1987 m²/g and total macropore surface area ofapproximately 723 m²/g). Support C had a total Langmuir surface area ofapproximately 1100 m²/g (including total micropore surface area ofapproximately 876 m²/g and total macropore surface area of approximately332 m²/g).

The candidate pore blocking compounds were 1,4-cyclohexanedione,ethylene glycol, and the diketal product of a coupling reaction between1,4-cyclohexanedione and ethylene glycol (i.e., 1,4-cyclohexanedionebis(ethylene ketal)).

Support samples (30 g) were contacted with a solution of1,4-cyclohexanedione in ethylene glycol (6 g/40 g) at approximately 25°C. for approximately 60 minutes. The pH of the slurry was adjusted toapproximately 1 by addition of concentrated hydrochloric acid andagitated by stirring for approximately 60 minutes. The pH of the slurrywas then adjusted to approximately 8.5 by addition of 50 wt. % sodiumhydroxide solution. The slurry was then filtered to isolate the treatedsupport, which was washed using deionized water at a temperature ofapproximately 90° C. (mechanism one)

Support samples (2 g) were also contacted with a solution of1,4-cyclohexanedione bis(ethylene ketal) in water (0.6 g/40 g) atapproximately 25° C. for approximately 60 minutes. (mechanism two)

As controls, samples of carbon A were also separately treated by contactwith (1) ethylene glycol and (2) 1,4-cyclohexanedione.

The treated supports were analyzed by the well-known Langmuir method todetermine their surface area (SA) profiles (e.g., total surface area,surface area attributed to micropores, and surface area attributed tomacropores). The results are shown in Table 1.

TABLE 1 % of original % of original Support Mechanism micropore SAmacropore SA Carbon A One 24.2 74.9 Carbon A Two 34.4 70.9 Carbon AControl One 93.7 98.7 Carbon A Control Two 68.9 94.4 Carbon B One 55.678.7 Carbon B Two 65.4 81.5 Carbon C One 17.9 76.8 Carbon C Two 22 72.3

As shown, both mechanism one and mechanism two provided a reduction inmicropore and macropore surface areas for each of supports A-C, and moreparticularly a greater reduction in micropore surface area as comparedto the reduction in macropore surface area (e.g., a three times greaterreduction in micropore surface area). The percentage reduction insurface area for carbon B is believed to be lower than that observed forthe other two carbons because of its higher surface area. However, itshould be noted that the percentage of micropore surface area reductionfor carbon B nonetheless corresponds to an absolute reduction ofapproximately 900 m²/g.

The control testing of carbon A with ethylene glycol provided minimalreduction in micropore and macropore surface areas, while the controltesting with 1,4-cyclohexanedione provided a greater reduction inmicropore and macropore surface areas, but to a much lesser degree thanassociated with both mechanism one and mechanism two. Thus, it isbelieved that the components combine to form the pore blocking compoundthat provides greater reduction in surface area than either componentalone or the cumulative reduction provided by each.

Example 2

Carbons A, B, and C (30 g) described in Example 1 were each treated bycontacting with solutions of 1,4-cyclohexanedione in ethylene glycol (6g/40 g) at approximately 25° C. for approximately 60 minutes. Eachcarbon was also treated by contacting with solutions of1,3-cyclohexanedione in ethylene glycol (1 g/50 g) at approximately 25°C. for approximately 120 minutes. Carbon C was also treated bycontacting with a solution of 1,4-cyclohexanedione in 1,2-propanediol (1g/50 g) at approximately 25° C. for approximately 60 minutes. Surfacearea analysis results are shown in Table 2. As shown, each combinationof dione and diol provided reduction of micropore and macropore surfaceareas, and more particularly preferential reduction in micropore surfacearea.

TABLE 2 % of original % of original Sample Dione Diol micropore SAmacropore SA Carbon A 1,4- Ethylene 22.6 75.8 disubstituted GlycolCarbon A 1,3- Ethylene 58.4 84 disubstituted Glycol Carbon B 1,4-Ethylene 55.6 78.7 disubstituted Glycol Carbon B 1,3- Ethylene 32.2 39.8disubstituted Glycol Carbon C 1,4- Ethylene 17.9 76.8 disubstitutedGlycol Carbon C 1,3- Ethylene 45 75.6 disubstituted Glycol Carbon C 1,4-1,2- 14.4 67.5 disubstituted Propanediol Carbon C 1,3- 1,2- 56.1 80.7disubstituted Propanediol

Example 3

This example provides transmission electron microscopy results (TEM) fora platinum on carbon catalyst prepared using Carbon B treated asdescribed in Example 1 (mechanism one). The catalyst containedapproximately 5 wt. % platinum and was prepared generally as detailedherein (e.g., by liquid phase deposition of platinum onto the treatedcarbon support), followed by treatment at elevated temperatures in anon-oxidizing environment. For comparison purposes, a catalyst including5 wt. % platinum on Carbon B that was not treated was also analyzed. TheTEM analysis was conducted generally as described by Wan et al. inInternational Publication No. WO 2006/031198.

The results for the catalyst including the untreated and treated carbonsare shown in FIGS. 3A/5A and 3B/5B, respectively. These results suggesta reduction in relatively small platinum-containing particles (e.g.,having a particle size less than 4 nm) for the catalyst prepared usingthe treated support.

The TEM results generally correspond to high density regions of thesubstrates including primarily micropores and these results indicatehigher platinum density among these regions for the catalyst includingthe untreated support.

Example 4

This example provides surface area analysis results for a carbon supportof the type described in U.S. Pat. Nos. 4,624,937 and 4,696,771 to Chouet al. (designated MC-10) treated in accordance with the presentinvention. Support samples were treated in accordance with bothmechanism one and mechanism two described above in Example 1. Thesupport had an initial micropore Langmuir surface area of approximately1987 m²/g and an initial macropore Langmuir surface area ofapproximately 723 m²/g. Micropore and macropore surface area retentionresults for the treated supports are shown in Table 3.

TABLE 3 Plugging % of original % of original Support Mechanism microporeSA macropore SA MC-10 One 55.6 78.7 MC-10 Two 65.4 81.5

FIGS. 4A and 4B provide pore volume data for untreated and treated MC-10supports.

Example 5

This example provides results of carbon monoxide (CO) chemisorptionanalysis for the platinum-containing catalysts of Example 4. COchemisorption is an analysis method suitable for estimating theproportion of exposed metal, and the analysis was conducted generally inaccordance with “Protocol A” described in Example 67 herein and Example23 of WO 2006/031938, incorporated herein by reference.

The results are shown in Table 4. The lower CO chemisorption for thecatalyst including a treated carbon support (38.6 and 43.3 μmol CO/gramversus 54.7 μmol CO/gram catalyst) indicate a reduced proportion ofexposed noble metal for the platinum-containing catalyst prepared usingthe treated carbon support.

TABLE 4 Cycle 2 Catalyst CO μmol/g catalyst Pt on regular MC-10 54.7 Pton modified MC-10 38.6/43.3

Example 6

Catalysts containing approximately 5 wt. % Pt and approximately 0.5 wt.% Fe were prepared generally as detailed herein using untreated MC-10carbon supports, and MC-10 carbon supports treated in accordance withboth mechanism one and mechanism two described in Example 1. Thesecatalysts were tested in PMIDA oxidation generally under the conditionsset forth in Example 7; the results are shown in Table 5. The Catalyst(1) included an untreated support. Catalysts (2) and (3) each includedsupports treated in accordance with mechanism two detailed above inExample 1. Catalyst (2) was prepared by a method that includedfiltration of the copper-impregnated support prior to platinumdeposition. Catalyst (3) was prepared by a method that did not includefiltration of the copper-impregnated support prior to platinumdeposition (i.e., a one-pot method as described in Example 16).

TABLE 5 Run Number 1 2 3 4 5 6 Catalyst (1) Run Time, 43.0 46.2 47.850.6 50.8 52.0 min GLY wt. % 5.413 5.600 5.620 5.678 5.556 5.748 PMIDAwt. % 0.034 0.034 0.094 0.134 0.075 0.149 CH₂O wt. % 0.150 0.182 0.1990.211 0.190 0.209 FORMIC 0.384 0.455 0.521 0.516 0.505 0.512 wt. % IDAwt. % 0.074 0.046 0.031 0.030 0.030 0.027 Pt in 0.03 0.07 0.07 0.09 0.080.12 soln. (ppm) Fe in 5.4 1.9 2.3 2.3 2.0 1.6 soln. (ppm) Catalyst (2)Run Time, 43.0 45.1 48.8 47.2 47.6 48.3 min GLY wt. % 5.363 5.543 5.5415.592 5.557 5.604 PMIDA wt. % 0.036 0.097 0.022 0.129 0.154 0.177 CH₂Owt. % 0.125 0.143 0.105 0.139 0.144 0.169 FORMIC 0.389 0.456 0.435 0.4790.484 0.508 wt. % IDA wt. % 0.086 0.052 0.041 0.033 0.031 0.028 Pt in0.05 0.14 soln. (ppm) Fe in 6.3 1.9 soln. (ppm) Catalyst (3) Run Time,43.0 46.3 46.7 48.5 48.5 49.8 min GLY wt. % 5.475 5.596 5.543 5.6495.790 5.980 PMIDA wt. % 0.058 0.141 0.167 0.136 CH₂O wt. % 0.175 0.1710.192 0.191 0.208 0.222 FORMIC 0.466 0.505 0.547 0.565 wt. % IDA wt. %0.073 0.044 0.030 0.026 0.025 0.022 Pt in soln. (ppm) Fe in soln. (ppm)GLY = Glyphosate FORMIC = Formic Acid IDA = Iminodiacetic Acid ppm =Parts Per MillionII. Catalyst Precursors; First and Second Metal-Containing Catalysts;Catalyst Precursor Structures

The following Examples describe preparation of catalysts as detailedherein, their testing by various characterization methods, and theirtesting in PMIDA oxidation. The following Examples also providecomparisons of catalysts prepared as detailed herein, and various othermetal-containing carbon-supported catalysts. For example, the followingExamples provide comparisons to carbon-supported catalysts including 5wt. % Pt, 0.1 wt. % Fe, and 0.4 wt. % Co, and carbon-supported catalystsincluding 5 wt. % Pt and 0.5 wt. % Fe. These catalysts were preparedgenerally as described by Wan et al. in International Publication No. WO2006/031938.

Example 7

Catalysts prepared as described herein and comparison samples weretested in PMIDA oxidation conditions also generally described by Wan etal. in International Publication No. WO 2006/031938. For example, PMIDAoxidation cycles were conducted in a glass reactor (200 ml commerciallyavailable from Ace Glass Inc.) containing a reaction mass (approx. 140g) which included water (approx. 128 g), approximately 8.2 wt. % PMIDA(approx. 11.48 g), and a catalyst loading of approximately 0.18 wt. %(0.25 g). The oxidations were generally conducted at a temperature ofapproximately 100° C., under a pressure of approximately 60 psig, and anoxygen flow rate of approximately 100 cc/min. Unless noted otherwise,reaction cycles were conducted to an endpoint determined by generationof approximately 1600 cm³ of carbon dioxide.

As described in the following Examples and accompanying figures, variousdata were collected, including cycle time, metal leaching, residualformaldehyde (HCHO) content, residual formic acid (HCOOH) content,iminodiacetic acid (IDA) formation, N-methyl-N-(phosphonomethyl)glycine(NMG) formation, total carbon dioxide (CO₂) generation, etc.

Example 8

This example details preparation of a catalyst containing a nominal Ptcontent of approximately 2.5 wt. % and a nominal Cu content ofapproximately 5 wt. % Cu on an activated carbon support having aLangmuir surface area of approximately 1500 m²/g.

Activated carbon (approx. 10 g), CuSO₄.5H₂O solution (approx. 2.07 g),sucrose (approx. 5.67 g), degassed deionized water (approx. 30 g), anddegassed 1M NaOH (70 g) were mixed in a baffled beaker. The mixture wasagitated at ambient conditions (approx. 25° C.) for approx. 20 minutes.Formaldehyde (approx. 2.25 g of 37 wt. % solution) was added to themixture and the resulting slurry was heated to approx. 30° C. andagitated for approx. 60 minutes.

The resulting slurry was filtered, washed with degassed deionized water,re-slurried in deionized water, and 1M HCl was added to provide a pH ofapprox. 1.5.

A solution of K₂PtCl₄ (approx. 0.557 g) in degassed water (15 g) wasadded to the slurry, followed by continued stirring for 60 minutes atambient conditions. The slurry was filtered, and the recoveredmetal-impregnated support was washed with water, and dried under vacuumat approx. 110° C. A total of 12.12 g of dried metal-impregnated supportwas recovered. Elemental analysis indicated a composition of approx.2.04 wt. %. Pt and approx. 1.93 wt. % Cu on carbon.

The catalyst precursor was then heated at elevated temperatures up toapproximately 815° C. in the presence of a hydrogen/argon stream(2%/98%; v/v) for approximately 60 minutes. Elemental analysis indicatedfinal metal contents of approx. 2.34% wt. Pt and approx. 2.22 wt. % Cu.

As detailed below, catalysts prepared by heating the metal-impregnatedsupport at varying temperatures were also tested. In addition, variousmetal-impregnated supports were also tested for their catalyticactivity.

Example 9 Copper Plating at Ambient Temperature

Preparation of nominal 2% Pt/3.45% Cu on activated carbon catalyst: Thefollowing were added to a baffled beaker including approx. 10 g ofactivated carbon: CuSO₄.5H₂O solution (1.410 g), 3.866 g of sucrose, 90g of degassed deionized water, and 5.974 g of 50 wt. % NaOH. The mixturewas stirred at approx. 22° C. for approx. 10 minutes using a mechanicalagitator. Following stirring, approx. 1.468 g of 37 wt. % formaldehydesolution was added and the resulting slurry was stirred at approx. 22°C. for 60 minutes. The slurry was then filtered and washed twice in thefilter, and then re-slurried in water to pH of approx. 2.0 by additionof 1.5M degassed HCl. To this slurry was added a solution of K₂PtCl₄(0.444 g) in 15 g of degassed water, followed by stirring forapproximately 60 minutes under ambient conditions. The slurry was thenheated to approx. 65° C., followed by stirring for an additional 30minutes. The resulting slurry was then filtered and washed with waterand dried under vacuum at approx. 110° C. A total of 11.389 g of driedmaterial was recovered.

Example 10

Preparation of nominal 2.5% Pt/5% Cu on activated carbon: The followingwas added to approx. 10 g of activated carbon in a baffled beaker: 2.072g of a CuSO₄.5H₂O solution, 5.694 g of sucrose, 30 g of degasseddeionized water, and 70 g of degassed 1M NaOH was added. The mixture washeated to approx. 35° C. using a mechanical agitator. To this mixturewas added 2.249 g of 37 wt. % formaldehyde solution and the resultingslurry was heated to approx. 33-35° C., followed by continued stirringfor 60 minutes. The slurry was filtered and washed with degasseddeionized water in the filter, and then re-slurried in water at pH ofapprox. 1.5 by adding 0.5M HCl. A solution of 0.557 g of K₂PtCl₄ in 15 gof degassed water was then added to the slurry, followed by continuedstirring for 60 minutes under ambient conditions. Then the slurry washeated to approx. 60° C. and stirred for an additional 30 minutes. Theresulting slurry was filtered and washed with water, and dried undervacuum at approx. 110° C. A total of 11.701 g of dried material wasrecovered. Upon heat treatment to a maximum temperature of approx. 950°C. in the presence of an argon/hydrogen atmosphere (2%/98%) (v/v) for120 minutes, a final catalyst composition indicating a weight loss ofapproximately 12.1 wt. % during heating was recovered.

Example 11 No Washing after Copper Deposition

Preparation of nominal 2% Pt/4% Cu on activated carbon: The followingwas added to a baffled beaker including approx. 10 g of activatedcarbon: 1.643 g of CuSO₄.5H₂O solution, 4.509 g of sucrose, 90 g ofdegassed deionized water, and 4.625 g of 50 wt. % NaOH. The mixture washeated to approx. 30° C. for approx. 10 minutes with a mechanicalagitator. To this slurry was added 1.706 g of 37 wt. % formaldehydesolution and the resulting slurry was heated to approx. 30-35° C.,followed by continued stirring for approx. 90 minutes. Then the slurrywas filtered, and then without washing re-slurried in water to pH 2.02by adding 1M degassed HCl. A solution of 0.454 g of K₂PtCl₄ in 10 g ofdegassed water was then added to the slurry, followed by continuedstirring for 60 minutes at ambient conditions. The resulting slurry wasthen heated to approx. 60° C. and stirred for an additional 30 minutes.This slurry was then filtered and washed with water, and dried undervacuum at approx. 110° C. A total of 11.720 g of dried material wasrecovered. During heat treatment to a maximum temperature ofapproximately 950° C. in the presence of an argon/hydrogen atmosphere(2%/98%) (v/v) for approximately 120 minutes, the sample lostapproximately 13.5% weight.

Example 12

Preparation of nominal 2% Pt/3.75% Cu on activated carbon: The followingwas added to a baffled beaker including approx. 10 g of activated carbon1.533 g of CuSO₄.5H₂O solution, 4.210 g of sucrose, 90 g of degasseddeionized water, and 4.300 g of 50 wt. % NaOH was added. This mixturewas heated to approx. 30° C. and stirred for approx. 10 minutes using amechanical agitator. To this mixture was added 1.507 g of 37 wt. %formaldehyde and the slurry was heated to approx. 30-35° C., followed bycontinued stirring for 60 minutes. The slurry was filtered and therecovered solids washed once in the filter, and then re-slurried inwater to a pH of 1.97 by adding 1M degassed HCl. A solution of 0.452 gof K₂PtCl₄ in 10 g of degassed water was then added to the slurry,followed by continued stirring for 60 minutes under ambient conditions.Then the slurry was heated to approx. 60° C. and stirred for 30 moreminutes. The slurry was filtered and washed with water, dried undervacuum at approx. 110° C. A total of 11.413 g of dried material wasrecovered. Upon heat treatment to a maximum temperature of approximately950° C. in the presence of a 2%/98% (v/v) H₂/Ar atmosphere for 120minutes, the sample lost approximately 12.5% weight.

Example 13 Platinum Deposition at Higher Temperature

Preparation of nominal 2% Pt/4% Cu on activated carbon: The followingwere added to a baffled beaker including 10 g of activated carbon: 1.645g of CuSO₄.5H₂O solution, 4.502 g of sucrose, 90 g of degassed deionizedwater, and 4.636 g of 50 wt. % NaOH. The mixture was stirred underambient conditions for approx. 20 minutes with a mechanical agitator.Then 1.721 g of 37% formaldehyde was added and the slurry was heated toapprox. 30-35° C., followed by continued stirring for 70 minutes. Thenthe slurry was filtered and washed once in the filter, and thenre-slurried in water to pH 2.95 by adding 1M degassed HCl. A solution of0.455 g of K₂PtCl₄ in 10 g of degassed water was then added to theslurry, followed by continued stirring for 45 minutes at 40-45° C. Thenthe slurry was heated to 60° C. and stirred for 30 more minutes. Theslurry was filtered and the recovered solids washed with water, anddried under vacuum at approx. 110° C. A total of 12.008 g of driedmaterial was recovered. Upon heat treatment at a maximum temperature ofapprox. 950° C. in the presence of a (2%/98%) (v/v) H₂/Ar atmosphere forapprox. 120 minutes, the sample lost approximately 12.6% weight.

Example 14

Preparation of nominal 3% Pt/6% Cu on activated carbon: The followingwere added to a baffled beaker including 10 g of activated carbon: 2.507g of CuSO₄.5H₂O solution, 6.878 g of sucrose, 90 g of degassed deionizedwater, and 6.974 g of 50 wt. % NaOH. The mixture was heated to 30° C.and stirred for approx. 10 minutes with a mechanical agitator. Then2.444 g of 37% formaldehyde was added and the slurry was heated toapprox. 35-37° C., followed by continued stirring for 45 minutes. Thenthe slurry was filtered and washed twice in the filter, and thenre-slurried in water to pH 1.97 by adding 1M degassed HCl. A solution of0.700 g of K₂PtCl₄ in 20 g of degassed water was then added to theslurry, followed by continued stirring for 60 minutes under ambientconditions. Then the slurry was heated to 60° C. and stirred for anadditional 30 minutes. The slurry was then filtered and washed withwater, and dried under vacuum at approx. 110° C. A total of 11.868 g ofdried material was recovered. Upon heat treatment at a maximumtemperature of approx. 950° C. in the presence of (2%/98%) (v/v) H₂/Aratmosphere for 120 minutes, the sample lost approximately 12.5% weight.

Example 15 Higher Platinum Content and Platinum Deposition Temperature

Preparation of nominal 4% Pt/8% Cu on activated carbon: The followingwere added to a baffled beaker including approx. 10 g of activatedcarbon: 3.420 g of CuSO₄.5H₂O solution, 9.375 g of sucrose, 100 g ofdegassed deionized water, and 9.675 g of 50 wt. % NaOH. The mixture washeated to 30° C. and stirred for 10 minutes with a mechanical agitator.Then 3.331 g of 37% formaldehyde was added and the resulting slurry washeated to approx. 30-35° C., followed by continued stirring for 90minutes. Then the slurry was filtered and washed once in the filter, andthen re-slurried in water to pH 1.97 by adding 1M degassed HCl. Asolution of 0.964 g of K₂PtCl₄ in 20 g of degassed water was then addedto the slurry, followed by continued stirring for 45 minutes at 45° C.Then the slurry was heated to 60° C. and stirred for an additional 45minutes. The slurry was then filtered and washed with water, and driedunder a vacuum at approx. 110° C. A total of 12.283 g of dried materialwas recovered. Upon heat treatment to a maximum temperature of approx.950° C. in the presence of a 2%/98% (v/v) H₂/Ar atmosphere for 120minutes, the sample lost approximately 12.6% weight.

Example 16 One-Pot Recipe

Preparation of nominal 2% Pt/4% Cu on activated carbon: The followingwere added to baffled beaker including 10 g of activated carbon: 1.644 gof CuSO₄.5H₂O solution, 4.509 g of sucrose, 90 g of degassed deionizedwater, and 4.715 g of 50 wt. % NaOH. The mixture was heated to 30° C.and stirred for 10 minutes with a mechanical agitator. Then 1.736 g of37% formaldehyde was added and the slurry was heated to approx. 30-35°C., followed by continued stirring for 90 minutes. Then the slurry wasacidified to pH 2.98 by adding 1M degassed HCl. A solution of 0.454 g ofK₂PtCl₄ in 10 g of degassed water was then added to the slurry, followedby continued stirring for 60 minutes at ambient conditions. Then theslurry was heated to 60° C. and stirred for 30 more minutes. The slurrywas then filtered and washed with water, and dried under vacuum atapprox. 110° C. A total of 11.864 g of dried material was recovered.Upon heat treatment at approx. 950° C. in the presence of a (2%/98%)(v/v) H₂/Ar for 120 minutes, the sample lost approximately 12.2% weight.

Example 17

Preparation of nominal 2% Pt/4% Cu on activated carbon: The followingwere added to a baffled beaker including 10 g of activated carbon: 1.645g of CuSO₄.5H₂O solution, 4.509 g of sucrose, 90 g of degassed deionizedwater, and 4.630 g of 50 wt. % NaOH. The mixture was heated to 30° C.and stirred for 10 minutes with a mechanical agitator. Then 1.710 g of37% formaldehyde was added and the slurry was heated to approx. 30-35°C., followed by continued stirring for 90 minutes. Then the slurry wasfiltered and washed once in the filter, and then re-slurried in water topH 2.01 by adding 1M degassed HCl. A solution of 0.570 g of H₂PtCl₆ in15 g of degassed water was then added to the slurry, followed bycontinued stirring for 60 minutes at ambient conditions. Then the slurrywas heated to 60° C. and stirred for an additional 30 minutes. Theslurry was then filtered and washed with water, and dried under vacuumat approx. 110° C.

Example 18

Preparation of nominal 2% Pt/4% Cu on activated carbon: The followingwere added to a baffled beaker including approx. 10 g of activatedcarbon: 1.644 g of CuSO₄.5H₂O solution, 4.517 g of sucrose, 70 g ofdegassed deionized water, and 4.701 g of 50 wt. % NaOH. The mixture washeated to 30° C. and stirred for approx. 10 minutes with a mechanicalagitator. Then 1.705 g of 37% formaldehyde diluted to 17.10 g withdegassed water was added, and the slurry was heated at approx. 30-35°C., followed by continued stirring for 60 minutes. Then the slurry wasfiltered and washed once in the filter, and then re-slurried in water topH 1.99 by adding 1M degassed HCl. A solution of 0.460 g of K₂PtCl₄ in10 g of degassed water was then added to the slurry, followed bycontinued stirring for 60 minutes at ambient conditions. Then the slurrywas heated to 60° C. and stirred for 30 more minutes. It was thenfiltered and washed with water, and dried under vacuum at approx. 110°C. A total of 11.203 g of dried material was recovered.

Example 19

This Example details surface area (SA) and CO chemisorption analysis forcatalysts of varying platinum and copper contents prepared generally inaccordance with the conditions detailed herein in Example 7, and testedin PMIDA oxidation for 10 cycles generally under the conditions setforth in Example 7.

TABLE 6 10 cycle 10 cycle 10 cycle spent spent 955° C.-120 10 cycle 10cycle 10 cycle 10 cycle 955° C.-120 955° C.-120 (temp/time) 955° C.-120955° C.-120 815° C.-60 955° C.-120 treated treated 2% Pt/ 3% Pt/ 2% Pt/2.5% Pt/ 2% Pt/ 2% Pt/ 2% Pt/ Description Average C 3.45% Cu/C 6% Cu/C3.45% Cu/C 7.5% Cu/C 4% Cu/C 4% Cu/C 3.75% Cu/C Langmuir SA 1499 13071208 1230 970 1236 1240 1254 (m²/g) t-plot micro SA 1193 1065 984 1002776 1019 1017 1034 (m²/g) Pore diameter 15.6 19.9 20.0 19.9 20.1 19.719.8 19.7 (Å) Meso-macro pore 293.184 235.358 220.629 223.477 189.809214.329 219.437 216.215 SA (m²/g)  20-40 175.666 147.013 137.710 139.592119.950 133.968 136.617 134.627  40-80 77.937 60.166 56.648 57.40848.620 54.628 56.582 55.397  80-150 25.781 18.164 16.873 16.961 13.80616.522 16.811 16.678  150-400 11.205 7.963 7.469 7.518 5.954 7.177 7.4637.468  400-1000 2.159 1.736 1.630 1.685 1.251 1.672 1.666 1.6801000-2000 0.396 0.315 0.297 0.313 0.228 0.331 0.298 0.315 2000-3000 0.040.001 0.002 0.000 0.000 0.031 0.000 0.050 Total meso-macro 293.184235.358 220.629 223.477 189.809 214.329 219.437 216.215 pore SA (m²/g)Pt(0) [μmol CO/g] NA 17.2 27.5 14.6 19.3 13.9 14.2 17.8 Total Pt NA 21.934.9 20 30.1 19.5 19.2 20.6 [μmol CO/g]

TABLE 7 10 cycle 10 cycle 10 cycle spent spent 955° C.-120 10 cycle 10cycle 10 cycle 10 cycle 955° C.-120 955° C.-120 Pore (temp/time) 955°C.-120 955° C.-120 815° C.-60 955° C.-120 treated treated diameterAverage C 2% Pt/ 3% Pt/ 2% Pt/ 2.5% Pt/ 2% Pt/ 2% Pt/ 2% Pt/ (Å) (3lots)3.45% Cu/C 6% Cu/C 3.45% Cu/C 7.5% Cu/C 4% Cu/C 4% Cu/C 3.75% Cu/C <4.00.0541 0.0475 0.0475 0.0474 0 0.0478 0.0379 0.0476 4.0-4.6 0.1072 0.08530.0758 0.0759 0.0952 0.0765 0.0851 0.0856 4.7-5.2 0.063 0.0568 0.04730.0567 0.0471 0.0572 0.0565 0.0569 5.3-6.0 0.063 0.0568 0.0566 0.04730.0356 0.0476 0.0472 0.0474 6.1-7.1 0.0465 0.0369 0.0454 0.0459 0.03290.0462 0.0459 0.0458 7.2-8.0 0.0346 0.0254 0.0241 0.0254 0.0239 0.02540.0331 0.025 8.1-9.0 0.0235 0.0224 0.0142 0.0221 0.0133 0.0226 0.02070.022  9.1-13.4 0.0589 0.0567 0.0538 0.0513 0.0424 0.0533 0.0498 0.051713.5-16.5 0.0216 0.017 0.016 0.0164 0.0129 0.0159 0.0196 0.019116.6-21.4 0.0274 0.0241 0.0248 0.023 0.0211 0.024 0.0214 0.021221.5-27.0 0.0254 0.021 0.018 0.02 0.0156 0.0174 0.0179 0.0176 total0.5252 0.4499 0.4235 0.4314 0.34 0.4339 0.4351 0.4399 micropore volume(cc/g)

FIG. 5C provides porosity data for each of the catalysts tested.

Example 20

This example provides surface area (SA) and pore volume (PV) analysisdata for a carbon support treated by contact with sucrose generally inaccordance with the method described below. Also provided are resultsfor a nominal 2% Pt/3.45% Cu/C catalyst prepared using a carbon supporttreated by contact with sucrose generally as described below, along withcopper and platinum deposition generally as described in Example 12. Themetal impregnated support was not subjected to elevated temperatures.

Carbon support (10 g) was added to a mixture including degassed H₂O(approx. 100 g), sucrose (approx. 3.8 g), 1M NaOH (approx. 6.15 g). Toprepare the sucrose mixture, the sucrose was first added to the waterfollowed by addition of NaOH, which was followed by addition of approx.1.9 g of 37 wt. % formaldehyde solution. After approximately 60 minutesat approximately 25° C., the mixture was acidified to pH ofapproximately 4.8 by addition of 2M HCl. The mixture was then stirredfor approximately 45 minutes at approximately 25° C., then filtered toisolate the support and the support was dried for approx. 10 hours in avacuum oven at a temperature of approx. 110° C. in the presence ofnitrogen. Approx. 11.5 g of treated support was recovered.

Both the catalyst and treated support were analyzed by surface area andpore volume analyses generally as described by Wan et al. inInternational Publication No. WO 2006/031938. The surface area and porevolume analysis results are shown in Tables 8 and 9, respectively. FIG.5D also provides the pore volume results.

TABLE 8 Sucrose Average Precursor, adsorbed onto Description Carbon 2%Pt/3.45% Cu/C Carbon Langmuir SA (m²/g) 1499 957 954 t-plot micro poreSA 1193 727 726 (m²/g) meso-macro pore SA 293.184 222.314 219.061 (m²/g)20-40 175.666 136.964 133.600 40-80 77.937 58.165 58.144  80-150 25.78117.608 17.651 150-400 11.205 7.676 7.743  400-1000 2.159 1.625 1.6721000-2000 0.396 0.276 0.251 2000-3000 0.04 0.000 0.000 total meso-macropore 293.184 222.314 219.061 SA (m²/g)

TABLE 9 Pore Average Sucrose diameter carbon Precursor, adsorbed onto(Å) (3 lots) 2% Pt/3.45% Cu/C carbon <4.0 0.0541 0.0191 0.0193 4.0-4.60.1072 0.0478 0.0483 4.7-5.2 0.063 0.0381 0.0385 5.3-6.0 0.063 0.04750.0385 6.1-7.1 0.0465 0.0366 0.0464 7.2-8.0 0.0346 0.0243 0.0171 8.1-9.00.0235 0.0197 0.0222  9.1-13.4 0.0589 0.0443 0.0465 13.5-16.5 0.02160.0182 0.0149 16.6-21.4 0.0274 0.0207 0.0238 21.5-27.0 0.0254 0.0180.0177 total 0.5252 0.3343 0.3332 micro PV (cc/g)

As shown in these results, reductions in total surface area, microporesurface area, and meso-/macropopre surface were approx. equivalent forthe catalyst in which sucrose was present in the copper deposition bath,and for the carbon support treated by contact with sucrose alone. Basedon these results, it is believed that a significant portion, if notsubstantially all, of the surface area reduction for the finishedcatalyst as compared to the starting support is based on the presence ofsucrose in the copper deposition bath.

Example 21

This example details microscopy results for the following samples:

-   (1) a carbon support having a total Langmuir surface of approx. 1500    m²/g (including micropore surface area of approx. 1200 m²/g and    meso-/macropore surface area of approx. 300 m²/g);-   (2) the carbon support of (1) containing a nominal copper content of    approx. 3.45 wt. % deposited generally in accordance with Example    12;-   (3) a nominal 2% Pt/3.45% Cu/C catalyst including support (1) and    prepared generally as described in Example 12, but prior to heating    at elevated temperatures;-   (4) the nominal 2% Pt/3.45% Cu/C catalyst of (3) after heating at    temperatures of approximately 950° C.

Microscopy analysis was generally conducted as described in Example 46.

Carbon Support

FIG. 6 is a STEM micrograph of the surface of the carbon support.

Cu-Impregnated Support

FIGS. 7 and 8 are STEM micrographs of the surface of the Cu-impregnatedsupport. These results indicate Cu regions of irregular morphology andsize deposited at the surface of the carbon support.

Pt/Cu-Impregnated Support (Prior to Heat Treatment)

FIGS. 9-12 are micrographs of the surface of the Pt/Cu impregnatedsupport prior to treatment at elevated temperatures. These resultsindicate regions of Cu deposited at the surface of the carbon supporthaving Pt deposited thereon that have generally retained the irregularmorphology and size of the deposited Cu regions.

FIG. 13 provides a STEM micrograph for a portion of the impregnatedsupport. The portion marked “Spectrum Image” was subjected to line scananalysis, the results of which are shown in FIG. 14. As shown, the linescan analysis indicates the presence of copper and platinum throughoutthe Spectrum Image portion.

Pt/Cu/C Catalyst (after Heating)

FIG. 15 is an STEM photomicrograph and FIG. 16 is a high resolution TEM(HRTEM) photomicrograph of a portion of the Pt/Cu/C catalyst afterheating at elevated temperatures. These Figures indicate a change in themorphology of the Pt/Cu regions. These results indicate formation ofspherical particles of sizes ranging from approx. 1 nm to approx. 15 nm.

FIGS. 17 and 18 are EDS spectra for particles of varying sizes. Asparticle size increases, the atom ratio of copper to platinum increases,indicating relatively constant amount of platinum among of theparticles. It is currently believed that thickness of the platinum layeris relatively constant over a range of particle size.

Pt/Cu/C Catalyst Used in 3 PMIDA Reaction Cycles

FIGS. 19-21 are STEM photomicrographs for a portion of a catalyst usedin 3 PMIDA reaction cycles under the above-noted conditions. Theseresults indicate the presence of stable particles of varying sizes,including those in the range of from approx. 1-1.5 nm.

FIG. 22 provides line scan data for the portion of the catalyst surfacemarked “Spectrum Image” in FIG. 21. Based on detection of Cu over theentire Spectrum Image, with the highest copper content at the center ofthe particle while the platinum signal remained relatively flat, theseresults suggest the presence of a relatively thin outerplatinum-containing shell (i.e., no more than 3 atoms thick). That is,since the line scan analysis utilized an X-ray beam of approx. 1 nm (10Å) in size this suggests the presence of a platinum-containing shellhaving a thickness of no more than 3 platinum atoms (atomic size ofplatinum is 3 Å).

Pt/Cu/C Catalyst Used in 30 PMIDA Reaction Cycles

These results are for catalysts tested for 30 reaction cycles. The STEMphotomicrographs of FIGS. 23 and 24 indicate the presence of stableparticles of varying sizes, including approx. 1-1.5 nm. FIG. 25 providesline scan data for the portion marked “Spectrum Image” in FIG. 24. Theseresults also indicate a relatively thin layer of platinum as both theplatinum and copper signals began to be detected at the same point bythe X-ray beam having a size of approx. 1 nm, again indicating thepresence of a platinum-containing shell less than 1 nm (i.e., less than3 platinum atoms) thick.

FIGS. 26 and 27 provide EDS spectra for particles of approx. 2 nm and 9nm in size. As shown, the atom percent of copper increased significantlywith particle size, including the presence of a copper-rich core.

Example 22

This example details results of microscopy analysis conducted generallyas described in Example 46 for: (1) a nominal 2% Pt/3.45% Cu/C catalystprecursor prepared as described in Example 9, and (2) a nominal 2%Pt/3.45% Cu/C catalyst prepared from the precursor (1) (e.g., heating ofthe precursor to a maximum temperature of approximately 950° C.).

FIGS. 28 and 29 are TEM and STEM images for precursor (1). FIGS. 30-37provide TEM images and corresponding line scan data for portions of theprecursor surface. As shown by the line scans, platinum and copper weredetected throughout the particle.

FIGS. 38 and 39 are TEM and STEM images for catalyst (2). FIGS. 40 and42 indicate the portion of the catalyst surface analyzed by line scans,the results of which are shown in FIGS. 41 and 43, respectively. Theline scan results indicate the presence of platinum throughout theparticles.

Example 23

This example provides particle size distribution analysis for a nominal2% Pt/3.45% Cu/C catalyst prepared as described in Example 9. Fifteenimages of the type shown in FIGS. 44 and 45 were used for determiningthe size of a total of 1177 particles. The size distribution of themeasured particles is shown in FIG. 46. This example also providesparticle size distribution analysis for the catalyst after use in PMIDAoxidation for 4 reaction cycles under the conditions described inExample 7. Fourteen images of the type shown in FIGS. 47 and 48 wereused to determine the size of 1319 particles. The size distribution ofthe measured particles is shown in FIG. 49.

Example 24

This example provides X-ray diffraction results for a nominal 2%Pt/3.45% Cu/C catalyst prepared as described in Example 12.

FIGS. 50 and 51 provide diffraction results for an area of the catalystsurface having a diameter of approximately 1 μm, measured using selectedarea electron diffraction (SAED). Based on the generation of FCC (facecentered cubic) indices (i.e., the results denoted 113, 022, 002, and111) and primitive cubic indices (i.e., the results denoted 300, 221,310, and 210), the SAED results indicate the presence of a CuPt alloyphase (likely a Cu₃Pt) alloy phase. The results may also indicate thepresence of a metallic copper phase.

FIGS. 52 and 53 provide nanodiffraction results from a single particleat the surface of the support. The nanodiffraction results are obtainedby focusing an X-ray beam having a diameter of approximately 50 nm indiameter on a portion of the catalyst surface. Based on the generationof primitive cubic indices (i.e., 010, 100, and 01-1), these resultsalso indicate the presence of a CuPt alloy phase (likely Cu₃Pt). Theindices denoted 200 and 11-1 are believed to be evidence of the presenceof a Cu phase, Pt phase, or further evidence of a CuPt alloy phase.FIGS. 54 and 55 highlight nanodiffraction results (the circled portions)indicating the presence of a metallic copper phase.

The following Examples 25-42 provide reaction testing data for variouscatalysts prepared generally as described in Examples 8-18. Variousparameters (e.g., metal loading, metal deposition temperature, and heattreatment temperature) were modified to determine the effect, if any, oncatalyst performance. Unless specifically noted otherwise, themetal-impregnated support was heated to a maximum temperature ofapproximately 955° C. in the presence of a hydrogen (2%)/argonatmosphere. The catalysts were generally tested in PMIDA oxidation underthe conditions set forth in Example 7.

Example 25

Catalysts: (1) 2.5% Pt/10% Cu; (2) 2.5% Pt/20% Cu; (3) 2.5% Pt/7.5% Cu;and (4) 5% Pt/0.1% Fe/0.4% Co. (nominal compositions)

FIG. 56 provides cycle time data for each of (1)-(4) for nine reactioncycles.

FIG. 57 provides platinum leaching data for (1) and (2) for each of ninereaction cycles.

Example 26

Catalysts: (1) 2.5% Pt/7.5% Cu; (2) 2.5% Pt/5% Cu; (3) 5% Pt/0.1%Fe/0.4% Co; and (4) 720° C./2.5% Pt/10% Cu. (nominal compositions)

FIG. 58 provides cycle time data for each of (1)-(4) for nine reactioncycles.

Example 27

Catalysts: (1) 2.5% Pt/10% Cu and (2) 720° C./2.5% Pt/10% Cu. (nominalcompositions)

Each catalyst was tested for 10 reaction cycles.

FIG. 59 provides cycle time data.

FIG. 60 provides IDA generation data.

FIGS. 61 and 62 provide residual formaldehyde and formic acidconcentration, respectively.

Table 10 provides a comparison of platinum leaching for the twocatalysts. As shown, less platinum was leached from the catalystprepared including heat treatment at 720° C.

TABLE 10 Pt/Parts per Million (ppm) Cycle 2.5% Pt10% Cu 720° C.-2.5%Pt10% Cu 1 0.103 <0.02 2 3 0.0715 <0.02 4 5 0.0539 <0.02 6 7 0.0514<0.02 8 9 0.0507 0.0202 10

Example 28

Catalysts: (1) 2.5% Pt/7.5% Cu; (2) 815° C./2.5% Pt/7.5% Cu; and (3) 5%Pt/0.1% Fe/0.4% Co. (nominal compositions) Each catalyst was tested fornine reaction cycles.

FIG. 63 provides cycle time data for each of (1)-(3).

FIGS. 64 and 65 provide residual formaldehyde and formic acidconcentration, respectively for each of (1)-(3).

Example 29

Catalysts: (1) 815° C./2.5% Pt/7.5% Cu; (2) 815° C./2.5% Pt/7.5% Cu; and(3) 5% Pt/0.1% Fe/0.4% Co. (nominal compositions) Each catalyst wastested for nine reaction cycles.

FIG. 66 provides cycle time data for each of (1)-(3).

FIGS. 67 and 68 provide residual formaldehyde and formic acidconcentration, respectively, for each of (1)-(3).

Example 30

Catalysts: (1) 815° C./2.5% Pt/7.5% Cu; (2) 815° C./2.5% Pt/5% Cu; (3)5% Pt/0.1% Fe/0.4% Co; (4) 815° C./2.5% Pt/3% Cu. (nominal compositions)Each catalyst was tested for ten reaction cycles.

FIG. 69 provides IDA generation results for each of (1)-(4).

FIGS. 70 and 71 provide residual formaldehyde and formic acidconcentration, respectively, for each of (1)-(4).

Example 31

Catalysts: (1) 815° C./2.5% Pt/5% Cu; (2) 715° C./2.5% Pt/5% Cu; (3)615° C./2.5% Pt/5% Cu; and (4) 5% Pt/0.1% Fe/0.4% Co. (nominalcompositions) Each catalyst was tested for ten reaction cycles andvarious parameters were compiled for nine or each of the ten reactioncycles.

FIG. 72 provides cycle time results.

FIGS. 73 and 74 provide residual formaldehyde and formic acidconcentrations, respectively.

FIG. 75 provides platinum leaching results.

FIG. 76 provides IDA generation results.

FIG. 77 provides NMG generation results.

FIG. 78 provides total CO₂ generation results.

Example 32

Catalysts: (1) 915° C./2% Pt/4% Cu (heated in a hydrogen containingatmosphere, i.e., reduced); (2) 910° C./2% Pt/4% Cu (heated in an inertatmosphere, i.e., calcined); and (3) 5% Pt/0.1% Fe/0.4% Co. (nominalcompositions) Each catalyst was tested for nine reaction cycles.

As shown in FIG. 79, cycle time was similar for each of (1)-(3), butcycle time for catalyst (3) was slightly higher for cycles 3 through 8.

FIG. 80 provides formaldehyde generation results.

FIG. 81 provides formic acid generation results.

As shown in FIG. 82, IDA generation was substantially equivalent foreach catalyst during cycles 3 through 9.

The results shown in FIG. 83 indicate reduced NMG generation for each ofthe 2% Pt catalysts as compared to the 5% Pt catalyst.

FIG. 84 provides total CO₂ generation results.

Example 33

This example provides platinum leaching results for the followingcatalysts: (1) 815° C./2.5% Pt/5% Cu; (2) 815° C./2.5% Pt/3% Cu; (3)910° C./2% Pt/4% Cu; (4) 908° C./2% Pt/3.6% Cu; and (5) 975° C./2%Pt/3.6% Cu. (nominal compositions). The results are shown in FIG. 85.

Example 34

This example provides testing results for catalysts in which thetemperature of copper deposition varied by approx. 10° C. (approx. 25°C. and approx. 35° C.) while the heat treatment temperature afterplatinum deposition was substantially similar.

Catalysts: (1) 970° C./2% Pt/3.45% Cu/35° C. and (2) 965° C./2% Pt/3.45%Cu/25° C. (nominal compositions)

As shown in FIGS. 86 and 87, formaldehyde and formic acid generationwere slightly lower for the catalyst prepared at the higher copperplating temperature.

The results shown in FIG. 88 indicate higher initial IDA generation forthe catalyst prepared at the higher copper plating temperature, butsimilar results for each catalyst beginning with the third cycle.

As shown in FIG. 89, platinum leaching was lower for the catalystprepared at the lower copper plating temperature. And FIG. 90 indicatesreduced initial copper leaching for the catalyst prepared at the lowercopper plating temperature.

Example 35

This example provides results for extended PMIDA oxidation testing over30 reaction cycles.

The catalysts tested included:

-   (1) nominal 2% Pt/3.45% Cu/C prepared as described in Example    12; (2) 5% Pt/0.1% Fe/0.4% Co; (3) nominal 2% Pt/3.45% Cu/C prepared    as described in Example 16; and (4) 5% Pt/0.5% Fe catalyst.

As shown in FIGS. 91-94, the cycle time, total CO₂ generation,formaldehyde generation, and formic acid generation were substantiallysimilar for each of (1)-(4). The catalyst loading was constant for eachcatalyst; thus, catalysts (1) and (3) provided similar results atreduced platinum loadings as compared to catalysts (2) and (4).

FIG. 95 provides Cu and Fe leaching data for catalysts (1), (3), and(4).

Example 36

This example provides PMIDA oxidation testing results for catalystsprepared at varying calcining temperatures and having varying coppercontents.

-   Catalysts: (1) 908° C./2% Pt/3.6% Cu; (2975°) C/2% Pt/3.6% Cu; (3)    910° C./2% Pt/4% Cu; and (4) 970° C./2% Pt/3.45% Cu. (nominal    compositions)

FIG. 96 provides IDA generation results.

FIGS. 97 and 98 indicate substantially similar results for formaldehydeand formic acid generation.

Example 37

This example provides reactor testing data for 2% Pt/4% Cu/C catalystsprepared generally as described in Example 11. Each catalyst was testedover 9 PMIDA reaction cycles.

One catalyst was prepared by heating the metal-impregnated support to amaximum temperature of approximately 950° C. in the presence of an inertargon atmosphere. A second catalyst was prepared by contacting themetal-impregnated support to a maximum temperature of approximately 950°C. in the presence of a hydrogen/argon (2%/98%) (v/v) atmosphere.

Cycle time and CO₂ generation data are provided for the two catalysts inTable 11. FIG. 99 shows cycle time for each catalyst.

TABLE 11 Cycle Calcined Calcined H₂-Reduced H₂-Reduced 1 2220 38.75 186750.92 2 2226 37.67 2077 42.33 3 2181 37.58 2109 39.42 4 2181 38 215537.08 5 2179 37.25 2095 40.42 6 2094 39.25 2136 37.42 7 2078 39.75 208939 8 2075 39 2067 38.5 9 2034 40.33 2060 37.42

Example 38

This example provides reactor testing data for a 2% Pt/4% Cu/C catalystand a 2% Pt/4% Cu/C metal-impregnated support (precursor) preparedgenerally as described in Example 11. The catalyst and metal-impregnatedsupport were tested over 4 PMIDA reaction cycles. The catalyst wasprepared by contacting a metal-impregnated support to a maximumtemperature of approximately 950° C. in the presence of a hydrogen/argon(2%/98%) (v/v) atmosphere.

Cycle time and CO₂ generation data are provided for the catalyst andmetal-impregnated support in Table 12. FIG. 100 shows cycle time foreach catalyst.

TABLE 12 Cycle Precursor Precursor Catalyst Catalyst 1 2003.4 36.921866.6 50.92 2 1912.5 39.17 2076.8 42.33 3 1841 41.58 2109.2 39.42

Example 39

This example provides a comparison of 2% Pt/4% Cu/C catalysts preparedusing different sources of platinum. Each catalyst was preparedgenerally as described in Example 11, including heating of ametal-impregnated support to a maximum temperature of approximately 950°C. Platinum was deposited by displacement deposition ontocopper-impregnated supports using platinum sources of: (1) K₂PtCl₄(i.e., Pt⁺² ions) and (2) H₂PtCl₆.H₂O (i.e., Pt⁺⁴ ions).

Table 13 provides cycle time, CO₂ generation data, and difference inactivity (based on cycle time) for each catalyst over 9 reaction cycles.FIGS. 101 and 102 provide cycle time and activity difference data.

TABLE 13 Cycle K₂PtCl₄ K₂PtCl₄ H₂PtCl₆ H₂PtCl₆ delta t % Activity 11866.6 50.92 1640.8 58.5 7.58 0.87 2 2076.8 42.33 1879.8 50.58 8.25 0.843 2109.2 39.42 1989.6 46.42 7 0.85 4 2155.1 37.08 1980.4 45.33 8.25 0.825 2095.1 40.42 1982 44.08 3.66 0.92 6 2135.9 37.42 1994.7 44.25 6.830.85 7 2089 39 1954.2 45.75 6.75 0.85 8 2066.8 38.5 1973.4 44.75 6.250.86 9 2059.6 37.42 1962.1 45.08 7.66 0.83 Total Cycle Total Cycle timeavg. 0.846 CO₂ time CO₂ excluding the 5th cycle

Example 40

This example provides CO chemisorption data (i.e., platinum sitedensity) for catalysts of varying platinum content prepared generally asdescribed in Examples 8, 11, 14, and 15. Table 14 provides the COchemisorption (determined generally in accordance with the methoddescribed in Example 67) and FIG. 103 provides a plot of platinumloading versus platinum site density. The catalysts were tested in PMIDAoxidation for 10 reaction cycles prior to CO chemisorption analysis.

TABLE 14 Chemisorption Cycle 2 Pt site density Pt loading (μmol CO/gcatalyst) 2 20.24 2.5 30.1 3 34.9 4 58

These results show a linear relationship between platinum loading andsite density. Based on these results, it is currently believed that asignificant portion of the platinum incorporated in the catalyst ispresent in the form of a relatively thin shell. Conversely, a non-linerrelationship between platinum loading and site density has been observedfor conventional platinum-containing catalysts. This is currentlybelieved to be due to the fact that a greater portion of the platinum isdistributed throughout metal particles. Thus, beyond certain level ofplatinum, loading platinum site density does not increase since theportion of platinum distributed throughout the particles does notcontribute to exposed platinum surface area.

Example 41

Catalysts containing nominal metal contents of approximately 2% Pt and4% Cu were prepared generally as described in Examples 11 and 12. Themetal deposition bath was maintained under a nitrogen atmosphere duringcopper deposition. Reaction testing results comparing the Pt/Cucatalysts to a 5% Pt/0.5% Fe catalyst are shown in FIG. 104. As shown,all catalysts provided comparable activity.

Example 42

This example details reaction testing of nominal 3% Pt/6% Cu catalystsprepared as described in Example 14 at varying catalyst loadings. Onecatalyst was tested at a catalyst loading of approximately 0.25 g andanother was tested at a loading of approximately 0.17 g. The performanceof each catalyst was compared to a 5% Pt/0.5% Fe catalyst preparedgenerally as described in U.S. Pat. No. 6,417,133 at a loading of 0.25g. Total catalyst and platinum loadings are summarized in Table 15.Total CO₂ generation results and cycle time results are shown in FIGS.105 and 106, respectively. As compared to the 5% Pt/0.5% Fe catalyst,these results indicate improved activity for the 3% Pt catalyst atequivalent catalyst loading and at least comparable activity at reducedcatalyst loading. Accordingly, 3% Pt catalysts of the present invention,or other similar catalysts, may be utilized to provide an improvement incatalyst activity, or a reduction in working metal capital.

TABLE 15 Reduction in Cat. Loading Reduction Pt loading Pt loadingCondition One 0.25 g 0% 0.0075 g 40% Condition Two 0.167 g  33%   0.005g 60% Control 0.25 g 0% 0.0125 g  0%III. Additional EmbodimentsDisodiumiminodiacetic Acid (DSIDA) Preparation

Example 43

This example details analysis and testing of: (1) a carbon-supportedpalladium and copper-containing catalyst (CuPdC) of the type describedin U.S. Pat. Nos. 5,916,840; 5,689,000, and/or 5,627,125; and (2) aCuPdC catalyst prepared as described in U.S. Pat. Nos. 5,916,840;5,689,000, and/or 5,627,125 that was treated by contact with a mixturecontaining 1,4-cyclohexane dione and ethylene glycol as described inExample 1 (mechanism 2).

The treated and un-treated catalysts were analyzed to determine theirLangmuir surface areas and to provide comparisons of the micropore andmacropore surface areas prior to and after treatment.

TABLE 16 % of original % of original Sample Dione Diol micropore SAmacropore SA Carbon A 1,4- Ethylene 22.6 75.8 disubstituted GlycolCarbon A 1,3- Ethylene 58.4 84 disubstituted Glycol Carbon B 1,4-Ethylene 55.6 78.7 disubstituted Glycol Carbon B 1,3- Ethylene 32.2 39.8disubstituted Glycol Carbon C 1,4- Ethylene 17.9 76.8 disubstitutedGlycol Carbon C 1,3- Ethylene 45 75.6 disubstituted Glycol Carbon C 1,4-1,2- 14.4 67.5 disubstituted Propanediol Carbon C 1,3- 1,2- 56.1 80.7disubstituted Propanediol

As shown in Table 16, treatment of the catalyst provided a 75% reductionin micropore surface area of the catalyst, while providing a reductionin macropore surface area of less than 20% (i.e., a preferentialreduction in micropore surface area approximately 4 times greater thanthe reduction in macropore surface area).

The treated and untreated catalysts were also tested for the conversionof diethanolamine to disodiumiminodiacetic acid. Mixtures includingwater, the (original or modified) catalyst (2 wt. %), diethanolamine(1.8 wt. %), sodium hydroxide (2.4 wt. %), and disodiumiminodiaceticacid (DSIDA) (12.5 wt. %) were heated to temperatures ranging from150-160° C. over the course of 5 hours and under a pressure ofapproximately 135 psig. These conditions were selected to determine theperformance of the modified and unmodified catalysts with regard tooxalate and glycine formation. The results are shown in FIG. 107. Themodified catalyst provided an approximately 8-10 fold reduction inoxalate formation and an approximately 4 fold reduction in glycinegeneration. These results suggest that the modified catalyst providedreduced exposed noble metal believed to contribute to glycine andoxalate formation.

Example 44

This example details testing of palladium and copper-containingcarbon-supported (CuPdC) catalysts in preparation of DSIDA bydehydrogenation of DEA. The catalysts were prepared as described in U.S.Pat. Nos. 5,916,840, 5,689,000, and/or 5,627,125 and tested generallyunder the conditions described therein. Two CuPdC catalysts wereprepared generally in accordance with the method described in one ormore of these patents. Each catalyst was prepared to include 24 wt. %Cu. One catalyst was prepared using an untreated carbon support; thisresulted in a catalyst including 3 wt. % Pd (i.e., 24% Cu/3% Pd/C). Thesecond catalyst was prepared using a carbon support treated by thepresent method as described in Example 1 by contact with 1,4-CHDM; thisresulted in a catalyst including approx. 2.4 wt. % Pd (i.e., 24% Cu/2.4%Pd/C). Thus, it is believed that use of the modified support resulted inreduced palladium deposition.

Each catalyst was tested in conversion of DEA to DSIDA generally inaccordance with the conditions set forth in U.S. Pat. Nos. 5,916,840,5,689,000, and/or 5,627,125. The results are shown in FIG. 108 and Table17.

As shown in FIG. 108, beginning with the second cycle, cycle time wasreduced for the catalyst including 2.4% Pd on the treated carbonsupport. That is, the catalyst prepared using the treated carbon supportprovided an increase in activity of approx. 15-20% at a lower noblemetal content.

TABLE 17 24% Cu on 2.4% Pd/ modified MC-10 24% Cu on 3% Pd/MC-10Hydroxy- Hydroxy- Cycle Oxalic ethyl Oxalic ethyl mol % Glycine AcidGlycine Glycine Acid Glycine 1 1.08 0.49 0.46 1.69 0.73 0.56 2 0.9 0.380.46 1.28 0.45 0.42 3 0.88 0.35 0.49 1.22 0.44 0.43 4 0.9 0.34 0.58 1.30.43 0.4 5 0.9 0.34 1.01 1.25 0.42 0.42 6 0.94 0.34 0.87 1.31 0.44 0.417 0.96 0.34 0.89 1.3 0.43 0.39 8 0.97 0.34 0.76 1.35 0.43 0.36 9 1.010.34 0.71 1.35 0.43 0.38 10 1.01 0.35 0.61 1.38 0.43 0.36

As shown in Table 17, use of the 2.4% Pd catalyst on the modified carbonsupport provided reduced oxalic acid generation and glycine generationas compared to the 3% Pd catalyst on the unmodified carbon support(e.g., an improvement in oxalic acid and glycine selectivities ofapprox. 15% and 25%, respectively).

IV. Platinum-Iron

Example 45

This example details preparation of a catalyst having a nominal platinumcontent of 2 wt. % and a nominal iron content of 4 wt. % on an activatedcarbon support having a Langmuir surface area of approximately 1500m²/g. The following preparation was conducted under nitrogen protection.

Activated carbon (approximately 10.458 g) and degassed water(approximately 90 g) were mixed in a baffled beaker under a nitrogenatmosphere. FeCl₃.xH₂O (2.007 g) was dissolved in degassed water (40 g)and this solution was pumped into the baffled beaker over a period ofone hour. The pH of the slurry within the baffled beaker was maintainedat 4 by introduction of 2.5N degassed NaOH, as necessary. After additionof the FeCl₃ solution was completed, the pH of the slurry was raised toapproximately 4.5 and the slurry was allowed to mix at room temperaturefor approximately 15 minutes. The slurry was then heated to atemperature of approximately 60° C. over a period of approximately 48minutes, during which time the pH of the slurry was maintained atapproximately 4.5 by addition of 2.5N NaOH.

The pH of the slurry was then raised to approximately 10.5 over a periodof approximately 30 minutes at a temperature of approximately 60° C.,and at a rate of 0.5 pH units per 5 minutes. After pH adjustment, theslurry was allowed to mix for approximately 10 minutes.

Sodium borohydride (NaBH₄) (approximately 0.686 g) was dissolved indegassed water (approximately 20 g); seven drops of 2.5N degassed NaOHwere added to stabilize the NaBH₄ solution, and the resulting NaBH₄solution was introduced to the baffled beaker at approximately 60° C.over a period of 20 minutes. The slurry was then allowed to mix for tenadditional minutes at approximately 60° C. The slurry was then filteredand the wet cake was then re-slurried in the baffled beaker in degasseddeionized water (approx. 90 g). The pH of the resulting slurry was thenlowered to approximately 5 by introduction of degassed 2M HCl.

K₂PtCl₄ (approximately 0.456 g) was dissolved in degassed water(approximately 20 g) and the resulting Pt solution was then added to thebaffled beaker over a period of three minutes. The resulting slurry wasthen allowed to mix at ambient conditions (approximately 22° C.) forapproximately 60 minutes, and then heated to a final temperature of 65°C. over a period of 30 minutes, and then allowed to mix at 60° C. Theresulting slurry was then filtered and washed twice by contact withdegassed water (approximately 100 g) at a temperature of approximately65° C. The washed sample was then dried in a vacuum oven atapproximately 110° C. for approximately 12 hours with a small nitrogenstream to form a Pt/Fe catalyst precursor.

The catalyst precursor was then heated at elevated temperatures up toapproximately 900° C. in the presence of a hydrogen/argon stream(2%/98%; v/v) for approximately 120 minutes.

The 2% Pt/4% Fe finished catalyst was tested in PMIDA oxidation underthe conditions set forth in Example 7. Inductively Coupled Plasma (ICP)analysis was used to determine platinum and iron leached from thecatalyst and present in the reaction mixture. ICP was conducted using aVG PQ ExCell Inductively Coupled Plasma-Mass Spectrometer (ICP-MS)(commercially available from Thermo Jarrell Ash Corp., Thermo Elemental,Franklin, Mass.). The results are set forth in Table 18.

FIG. 109 provides results of XRD analysis (conducted as set forth inExample 69) for the finished catalyst (i.e., before reactor testing).

TABLE 18 Cycle 1 2 3 4 5 6 7 8 9 10 Total CO₂ (cc) 1766.6 1871.4 1966.51946.8 1935.5 1957.5 1940.7 1947.9 1932.0 1600.6 End point(min) 45.0039.75 38.08 39.92 40.25 38.83 39.25 40.00 39.83 40.00 Maximum CO₂ 35.737.9 38.8 36.9 36.7 37.4 37.0 36.7 36.5 36.5 Concentration (%) PMIDA(wt. %) 0.008 0.010 0.010 0.010 0.010 0.034 Glyphosate(wt. %) 5.2935.378 5.400 5.393 5.392 5.563 IDA(wt. %) 0.099 0.065 0.051 0.045 0.0400.039 CH₂O(ppm) 2421 1990 1838 1660 1737 2309 HCOOH(ppm) 6696 6555 61436220 5716 6635 Pt(ppm) <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 Fe(ppm) 1.4840.494 <0.1 <0.1 <0.1 <0.1

Example 46

This example details preparation of a catalyst having a nominal platinumcontent of 2 wt. % and a nominal iron content of 4 wt. % on an activatedcarbon support having a Langmuir surface area of approximately 1500m²/g. The following preparation was conducted under nitrogen protection.

Activated carbon (approximately 10.455 g) and degassed water(approximately 90 g) were mixed in a baffled beaker under a nitrogenatmosphere. Fe₂(SO₄)₃.xH₂O (2.990 g) was dissolved in degassed water (40g) and this solution was pumped into the baffled beaker over a period ofone hour. The pH of the slurry within the baffled beaker was maintainedat 4 by introduction of 2.5N degassed NaOH, as necessary.

Mixing of the components of the slurry within the baffled beakeroccurred for a total of approximately 20 minutes at a pH ofapproximately 4. The pH of the slurry was then raised to 4.5 by additionof NaOH. The slurry was then heated to a temperature of approximately60° C. over a period of 30 minutes. During the heating, the pH wasmaintained at 4.5 by introduction of 2.5N degassed NaOH (as necessary).At this elevated temperature, the pH of the slurry was raised toapproximately 6.5 over a period of 20 minutes, via increases in pH at arate of approximately 0.5 pH units per 5 minutes.

Sodium borohydride (NaBH₄) (approximately 0.681 g) was dissolved indegassed water (approximately 20 g) and then pumped into the baffledbeaker at approximately 60° C. over a period of 20 minutes. The slurrywas then allowed to mix for ten additional minutes at 60° C. The slurrywas then allowed to cool to 45° C., and then filtered. The wet cake wasthen re-slurried in the baffled beaker in degassed deionized water (90g). The pH of the resulting slurry was then lowered to approximately 5by introduction of degassed 2M HCl.

K₂PtCl₄ (approximately 0.460 g) was dissolved in degassed water(approximately 20 g) and the resulting Pt solution was then added to thebaffled beaker over a period of five minutes. The resulting slurry wasthen allowed to mix under ambient conditions (approximately 22° C.) forapproximately 60 minutes, and then heated to a final temperature of 65°C. over a period of 30 minutes, and then allowed to mix at 65° C. for anadditional 10 minutes. The resulting slurry was then filtered and washedtwice by contact with degassed water (approximately 100 g) at atemperature of approximately 65° C. The washed sample was then dried ina vacuum oven at approximately 110° C. for approximately 12 hours with asmall nitrogen stream to form a Pt/Fe catalyst precursor.

The catalyst precursor was then heated at elevated temperatures up toapproximately 900° C. in the presence of a hydrogen/argon stream(2%/98%; v/v) for approximately 120 minutes.

Table 19 sets forth PMIDA reaction testing results, platinum leachingdata, and iron leaching data for the 2% Pt/4% Fe finished catalyst.

TABLE 19 Cycle 1 2 3 4 5 6 7 8 9 10 Total CO₂ (cc) 1912.0 1933.8 1951.21978.7 1944.0 1943.9 1956.3 1891.4 1864.9 1602.2 End point(min) 38.1737.33 36.75 35.67 37.75 37.50 37.67 39.50 40.83 40.17 Maximum CO₂ 40.539.6 39.9 41.3 38.8 39.6 39.0 37.8 36.7 37.2 Concentration (%) PMIDA(wt. %) ND 0.006 0.006 0.007 0.007 0.009 Glyphosate(wt. %) 5.184 5.2495.382 5.349 5.393 5.497 IDA(wt. %) 0.139 0.055 0.040 0.038 0.032 0.032CH₂O(ppm) 2586 2212 2203 2149 2300 2983 HCOOH(ppm) 5387 5525 6021 58435623 5958 Pt(ppm) 0.019 0.024 0.027 0.025 0.027 0.032 Fe(ppm) 16.4200.629 0.222 0.077 <0.05 <0.05

Example 47

This Example provides the results of X-Ray Diffraction (XRD) analysisfor the catalyst prepared as described in Example 46. XRD analysis wasconducted as set forth in Example 69.

The results are shown in FIGS. 110 and 111. These results indicate thepresence of Fe₃Pt bimetallic alloy.

Example 48

This example details preparation of a catalyst having a nominal Ptcontent of 2 wt. % and a nominal iron content of 4 wt. % on an activatedcarbon support having a Langmuir surface area of approximately 1500m²/g. The following preparation was conducted under nitrogen protection.

Activated carbon (approximately 10.455 g) and degassed water(approximately 90 g) were mixed in a baffled beaker under a nitrogenatmosphere.

FeCl₃.6H₂O (approximately 2.009 g) was dissolved in degassed water (40g) and this solution was pumped into the baffled beaker over a period ofone hour. The pH of the slurry within the baffled beaker was maintainedat 4 by introduction of 2.5N degassed NaOH, as necessary. After additionof the FeCl₃.6H₂O solution to the beaker was completed, the pH of theslurry was raised to approximately 4.5 by addition of NaOH and theslurry was allowed to mix at ambient conditions (approximately 22° C.)for approximately 20 minutes.

The slurry was then heated to a temperature of approximately 60° C. overa period of approximately 50 minutes. During the heating, the pH wasmaintained at 4.5 with addition of 2.5N degassed NaOH. At this elevatedtemperature, the pH of the slurry was raised to approximately 10.5 overa period of 30 minutes, via increases in pH at a rate of approximately0.5 pH units per 5 minutes.

Sodium borohydride (NaBH₄) (approximately 0.69 g) was dissolved indegassed water (approximately 20 g); 7 drops of 2.5N NaOH was added tostabilize the NaBH₄ solution. The sodium borohydride solution was thenpumped into the baffled beaker at approximately 60° C. over a period of20 minutes. The slurry was then filtered and the wet cake was thenre-slurried in the baffled beaker in degassed deionized water (90 g).The pH of the resulting slurry was then lowered to approximately 5 byintroduction of degassed 2M HCl.

K₂PtCl₄ (approximately 0.460 g) was dissolved in degassed water(approximately 20 g) and the resulting Pt solution was then added to thebaffled beaker over a period of three minutes. The resulting slurry wasthen allowed to mix at ambient conditions (approximately 22° C.) forapproximately 60 minutes, and then heated to a final temperature ofapproximately 65° C.

The resulting slurry was then filtered and washed twice by contact withdegassed water (approximately 100 g) at a temperature of approximately65° C. The washed sample was then dried in a vacuum oven atapproximately 110° C. for approximately 12 hours with a small nitrogenstream to form a Pt/Fe catalyst precursor.

The catalyst precursor was then heated at elevated temperatures up toapproximately 900° C. in the presence of a hydrogen/argon stream(2%/98%; v/v) for approximately 120 minutes.

Table 20 sets forth PMIDA reaction testing results, platinum leachingdata, and iron leaching data for the 2% Pt/4% Fe finished catalyst.

TABLE 20 Cycle 1 2 3 4 5 6 7 8 9 10 Total CO₂ (cc) 1738.2 1826.0 1846.21857.1 1866.1 1872.0 1878.0 1862.4 1875.6 1602.2 End point(min) 46.7542.50 42.08 41.67 41.50 41.58 41.50 42.25 42.00 42.58 Maximum CO₂ 34.435.3 35.6 35.7 35.7 35.6 35.9 35.3 35.4 35.0 Concentration (%) PMIDA(wt. %) 0.007 0.010 0.009 0.009 0.009 0.060 Glyphosate(wt. %) 5.3395.371 5.441 5.389 5.298 5.245 IDA(wt. %) 0.083 0.054 0.046 0.045 0.0420.041 CH₂O(ppm) 2158 1857 1669 1706 1682 1831 HCOOH(ppm) 7454 7161 69196648 6487 6941 Pt(ppm) 0.011 0.013 0.015 0.015 0.015 0.019 Fe(ppm) 3.1140.543 0.178 0.124 0.053 0.062 Cycle 11 12 13 14 15 16 17 18 19 20 21Total CO₂ (cc) 1875.8 1868.2 1878.2 1868.5 1855.9 1890.5 1872.9 1837.51854.1 1845.7 1830.5 End point(min) 41.33 42.33 42.25 42.67 43.58 42.0843.83 44.33 44.25 44.25 45.25 Maximum CO₂ 35.7 35.9 35.5 35.0 34.6 35.534.4 34.1 34.1 34.4 33.9 Concentration (%) PMIDA (wt. %) 0.009 0.0100.009 0.010 0.010 0.010 0.010 Glyphosate(wt. %) 5.315 5.405 5.406 5.3825.371 5.477 5.424 IDA(wt. %) 0.043 0.041 0.038 0.039 0.037 0.036 0.037CH₂O(ppm) 1898 2086 2067 2111 2173 2107 1853 HCOOH(ppm) 6159 6287 61996302 5805 6582 6175 Pt(ppm) 0.023 0.024 0.024 0.023 0.024 0.024 0.023Fe(ppm) <0.05 <0.05 0.054 <0.05 <0.05 <0.05 <0.05

FIG. 111A includes platinum leaching data for the catalysts of Examples46 and 48, as compared to a (Reference) 5% Pt/0.5% Fe catalyst preparedas described by Wan et al. in International Publication No. WO2006/031938.

Example 49

The following preparation was conducted under nitrogen protection.

Activated carbon (approximately 10.456 g) and degassed water(approximately 90 g) were placed in a baffled beaker and allowed to mixfor 20 minutes. FeCl₃.6H₂O (2.009 g) was dissolved in degassed water(approx. 40 g) and this solution was pumped into the baffled beaker overa period of 30 minutes while the pH of the slurry was maintained at 4 byaddition of 2.5N NaOH. After addition of the FeCl₃.6H₂O solution, the pHwas raised to 4.5 and allowed to mix for 10 minutes. The slurry was thenheated to approximately 50° C. over a period of 30 minutes, while the pHwas maintained at pH 4.5. The pH of the slurry was then raised to 8 overa period of 15 minutes, and allowed to mix for approximately 10 minutes.Ethylene glycol (approx. 1.386 g) was then added to the slurry, andallowed to mix at approximately 60° C. for approximately 20 minutes.After mixing was complete, the slurry was allowed to cool to 30° C.

The pH of the solution was then lowered to 5 by addition of 0.5Mdegassed HCl. K₂PtCl₄ (0.460 g) was dissolved in degassed water (20 g).The Pt solution was then added to the baffled beaker over a period ofthree minutes. The slurry was then allowed to mix at ambient conditions(approximately 22° C.) room temperature for 30 minutes, and then heatedto a temperature of 60° C. over a period of 10 minutes.

The slurry was then filtered, and the wet cake was hot washed twice at60° C. with approximately 100 mL of degassed water. The resulting samplewas then dried in a vacuum oven at 110° C. for 12 hours with a smallnitrogen stream.

Example 50

The following preparation was conducted under nitrogen protection.

Activated carbon (10.456 g) and degassed water (approximately 90 g) wereplaced in a baffled beaker and allowed to mix for 20 minutes. FeCl₃.6H₂O(2.011 g) was dissolved in degassed water (approximately 40 g) and thissolution was pumped into the baffled beaker over a period of 34 minuteswhile the pH of the slurry was maintained at 4 by addition of 2.5N NaOH.

Upon the complete addition of the FeCl₃.6H₂O solution, the pH was raisedto 4.5, and allowed to mix for 10 minutes. The slurry was then heated toapproximately 60° C. over a period of 34 minutes, while the pH wasmaintained at 4.5. The pH of the slurry was then raised to 11 over aperiod of 30 minutes, and then allowed to mix for 10 minutes. Ethyleneglycol (1.385 g) was then added to the slurry, and allowed to mix at 60°C. for approximately 10 minutes.

The pH of the solution was then lowered to 5 by addition of 1M degassedHCl. K₂PtCl₄ (0.459 g) was dissolved in degassed water (20 g). The Ptsolution was then added to the baffled beaker over a period of threeminutes. The slurry was then allowed to mix at ambient conditions(approximately 22° C.) for 30 minutes, and then heated to a temperatureof approximately 60° C. over a period of 10 minutes.

The slurry was then filtered, and the wet cake was hot washed twice at60° C. with approximately 100 ml of degassed water. The resulting samplewas then dried in a vacuum oven at 110° C. for 12 hours with a smallnitrogen stream.

Four 2% Pt/4% Fe catalysts were prepared from a precursor prepared asdescribed that was heated at elevated temperatures in the presence of ahydrogen/argon stream (4%/96%; v/v) for approximately 120 minutes.Maximum heating temperatures were:

-   (1) 900° C.;-   (2) 750° C.;-   (3) 650° C.;-   (4) 550° C.

FIG. 112 provides results of XRD analysis of catalyst (1); these resultsindicate the presence of a Fe₃Pt phase.

FIG. 113 provides results of XRD analysis of catalyst (2); these resultsindicate the presence of a Fe₃Pt phase.

FIG. 114 provides results of XRD analysis of catalyst (3); these resultsindicate the presence of a Fe₃Pt phase.

FIG. 115 provides results of XRD analysis of catalyst (4); these resultsindicate the presence of a FePt phase.

Reaction testing data, platinum leaching data, and iron leaching datafor the 900° C./2% Pt/4% Fe catalyst are set forth in Table 21.

TABLE 21 Cycle 1 2 3 4 5 6 7 8 Total CO₂ (cc) 1751.9 1793.3 1863.91930.6 1931.1 1946.4 1926.7 1602.3 End point(min) 44.08 43.00 41.6740.75 41.00 41.25 41.08 42.90 Maximum CO₂ 36.2 35.2 35.3 35.5 35.7 35.236.1 34.4 Concentration (%) PMIDA (wt. %) 0.003 0.006 0.006 0.006 0.104Glyphosate(wt. %) 5.243 5.398 5.486 5.376 5.539 IDA(wt. %) 0.079 0.0400.035 0.034 0.032 CH₂O(ppm) 3032 2513 2072 2156 2596 HCOOH(ppm) 63006615 6554 6358 6488 Pt(ppm) 0.011 0.014 0.014 0.013 0.017 Fe(ppm) 24.0503.309 0.494 0.462 0.409

Reaction testing data, platinum leaching data, and iron leaching datafor the 750° C./2% Pt/4% Fe catalyst are set forth in Table 22.

TABLE 22 Cycle 1 2 3 4 5 6 7 8 9 Total CO₂ (cc) 1812.9 1786.8 1854.81901.3 1864.6 1906.0 1921.1 1913.3 1601.9 End point(min) 39.92 42.5841.42 40.25 42.58 41.83 41.50 42.00 42.55 Maximum CO₂ 39.2 35.8 35.736.3 34.5 34.9 35.6 35.0 35.2 Concentration (%) PMIDA (wt. %) ND 0.0090.006 0.010 0.064 Glyphosate(wt. %) 5.275 5.357 5.464 5.471 5.528IDA(wt. %) 0.098 0.037 0.033 0.035 0.030 CH₂O(ppm) 2901 2398 2105 20102550 HCOOH(ppm) 6151 6628 6634 6640 6553 Pt(ppm) 0.013 0.015 0.016 0.0160.019 Fe(ppm) 24.870 3.516 0.686 0.476 0.356

Reaction testing data, platinum leaching data, and iron leaching datafor the 650° C./2% Pt/4% Fe catalyst are set forth in Table 23.

TABLE 23 Cycle 1 2 3 4 5 6 7 8 9 10 Total CO₂ (cc) 1782.0 1849.5 1908.81897.5 1957.4 1947.6 1878.0 1901.6 1913.4 1602.7 End point(min) 41.4240.67 39.33 39.75 39.08 38.00 42.25 41.50 41.08 42.23 Maximum CO₂ 38.736.7 37.2 36.8 37.7 39.7 34.9 35.5 36.1 35.3 Concentration (%) PMIDA(wt. %) ND 0.005 0.006 0.005 0.005 0.067 Glyphosate(wt. %) 5.229 5.3735.394 5.413 5.394 5.490 IDA(wt. %) 0.099 0.045 0.040 0.037 0.036 0.036CH₂O(ppm) 3042 2485 2357 2358 2395 2754 HCOOH(ppm) 6185 6634 6461 65216372 6512 Pt(ppm) 0.014 0.016 0.015 0.015 0.015 0.019 Fe(ppm) 25.2302.754 0.493 0.395 0.422 0.332

Reaction testing data, platinum leaching data, and iron leaching datafor the 550° C./2% Pt/4% Fe catalyst are set forth in Table 24.

TABLE 24 Cycle 1 2 3 4 5 6 7 8 9 Total CO₂ (cc) 1834.2 1842.8 1885.91881.2 1876.2 1891.8 1887.9 1842.3 1839.5 End point(min) 38.17 39.5838.58 39.08 40.25 39.67 40.17 42.00 42.08 Maximum CO₂ 41.0 38.1 38.638.0 36.7 37.5 37.3 35.8 35.8 Concentration (%) PMIDA (wt. %) 0.0030.007 0.006 0.007 0.009 Glyphosate(wt. %) 5.197 5.376 5.379 5.339 5.341IDA(wt. %) 0.095 0.049 0.044 0.041 0.037 CH₂O(ppm) 2670 2306 2018 22362425 HCOOH(ppm) 6221 7076 7141 7100 7033 Pt(ppm) 0.015 0.015 0.015 0.0160.016 Fe(ppm) 27.940 2.972 0.594 0.315 0.406

Example 51

The following preparation was conducted under nitrogen protection.

Activated carbon (approximately 10.456 g) and degassed water (approx. 90g) were placed in a baffled beaker and allowed to mix for approximately20 minutes.

FeCl₃.6H₂O (2.009 g) was dissolved in degassed water (approx. 40 g) andthis solution was then pumped into the baffled beaker over a period of30 minutes while the pH of the slurry was maintained at 4 by addition of2.5N NaOH. Upon complete addition of the FeCl₃.6H₂O solution, the pH wasraised to 4.5 and the slurry was allowed to mix for 10 minutes. Theslurry was then heated to 60° C. over a period of 30 minutes, while thepH was maintained at pH 4.5. The pH of the slurry was then raised to 6.5over a period of 10 minutes, and allowed to mix for 10 minutes. Ethyleneglycol (approx. 1.384 g) was then added to the slurry, and allowed tomix at approximately 60° C. for approximately 10 minutes. The slurry wasthen filtered, and the wet cake was then re-slurried in degasseddeionized water (90 g) and introduced into the baffled beaker.

The pH of the solution was then lowered to 5 by addition of degassed 1MHCl (0.841 g). K₂PtCl₄ (0.459 g) was dissolved in degassed water (20mL). The resulting Pt solution was then added to the baffled beaker overa period of three minutes. The slurry was then allowed to mix at ambientconditions (approximately 22° C.) for 30 minutes, and then heated to atemperature of 60° C. over a period of 10 minutes.

The slurry was filtered, and the wet cake was hot washed twice at 60° C.with approximately 100 mL of degassed water. The resulting sample wasthen dried in a vacuum oven at 110° C. for 12 hours with a smallnitrogen stream.

The catalyst precursor was then heated at elevated temperatures up toapproximately 755° C. in the presence of a hydrogen/argon stream(4%/96%; v/v) for approximately 120 minutes.

Example 52

The following preparation was conducted under nitrogen protection.

Activated carbon (approximately 10.456 g) and degassed water(approximately 90 g) were placed in a baffled beaker and allowed to mixfor 20 minutes. FeCl₃.6H₂O (2.411 g) was dissolved in degassed water(approximately 41 g) and this solution was then pumped into the baffledbeaker over a period of 30 minutes while the pH of the slurry wasmaintained at 4 by addition of 2.5N NaOH. Upon complete addition of theFeCl₃.6H₂O solution, the pH was raised to 4.5, and allowed to mix for 10minutes. The slurry was then heated to 60° C. over a period of 25minutes while the pH was maintained at pH 4.5. The pH of the slurry wasthen raised to 11 over a period of 30 minutes, and then allowed to mixfor 10 minutes.

Ethylene glycol (1.382 g) was then added to the slurry, and allowed tomix at approximately 60° C. for approximately ten minutes. The slurrywas then filtered, and the wet cake was then re-slurried in degasseddeionized water (90 g) and introduced into the baffled beaker.

The pH of the solution was then lowered to 5 by addition of degassed 1Mdegassed HCl (3.7 g). K₂PtCl₄ (0.552 g) was dissolved in degassed water(20 g) and the Pt solution was then introduced into the baffled beakerover a period of three minutes. The slurry was then allowed to mix atambient conditions (approximately 22° C.) for 30 minutes and then heatedto a temperature of 60° C. over a period of 10 minutes.

The slurry was then filtered, and the wet cake was hot washed twice at60° C. with approximately 100 mL of degassed water. The sample was thendried in a vacuum oven at 110° C. for 12 hours with a small nitrogenstream.

The catalyst precursor was then heated at elevated temperatures up toapproximately 650° C. in the presence of a hydrogen/argon stream(4%/96%; v/v) for approximately 120 minutes.

TABLE 24A Cycle 1 2 3 4 5 6 7 8 9 10 Total CO₂ (cc) 1944.2 1977.4 2048.32044.4 2055.9 2058.7 2054.7 2065.8 2037.7 1600.2 End point(min) 33.5834.92 34.08 35.58 35.50 35.58 35.42 35.25 35.83 37.67 Maximum CO₂ 44.541.3 41.8 39.8 39.5 40.0 40.2 41.0 40.6 37.8 Concentration (%) PMIDA(wt. %) ND 0.005 0.005 0.007 0.007 0.106 Glyphosate(wt. %) 5.121 5.3415.410 5.378 5.433 5.538 IDA(wt. %) 0.155 0.057 0.048 0.042 0.041 0.039CH₂O(ppm) 2625 2077 1897 1897 1659 2602 HCOOH(ppm) 5320 5891 5858 58005817 6283 Pt(ppm) 0.019 0.018 0.018 0.018 0.018 0.022 Fe(ppm) 30.1702.713 0.577 0.372 0.331 0.541

Example 53

The following preparation was conducted under nitrogen protection.

Activated carbon (10.456 g) and degassed water (approximately 90 g) wereplaced in a baffled beaker and allowed to mix for 20 minutes. FeCl₃.6H₂O(2.009 g) was dissolved in degassed water (approximately 41 g) and theresulting solution was pumped into the baffled beaker over a period of30 minutes while the pH of the slurry was maintained at 4 by addition of2.5N NaOH. After addition of the FeCl₃.6H₂O solution, the pH was raisedto 4.5, and allowed to mix for 10 minutes. The slurry was then heated toapproximately 50° C. over a period of 32 minutes, while the pH wasmaintained at pH 4.5. The pH of the slurry was then raised to 8 over aperiod of 15 minutes, and then allowed to mix for 10 minutes. Ethyleneglycol (1.386 g) was then added to the slurry, and allowed to mix at 60°C. for ten minutes. The slurry was then filtered, and the wet cake wasthen re-slurried in degassed deionized water (90 g) and introduced intothe baffled beaker.

The pH of the solution was then lowered to 5 by addition of degassed0.5M HCl (2.17 g). K₂PtCl₄ (0.460 g) was dissolved in degassed water (20g) and the Pt solution was then introduced into the baffled beaker overa period of three minutes. The slurry was then allowed to mix at roomtemperature for 30 minutes, and then heated to a temperature of 60° C.over a period of 10 minutes. The slurry was then filtered, and the wetcake hot washed twice at 60° C. with approximately 100 mL of degassedwater. The sample was then dried in a vacuum oven at 110° C. for 12hours with a small nitrogen stream.

The catalyst precursor was then heated at elevated temperatures up toapproximately 550° C. in the presence of a hydrogen/argon stream(4%/96%; v/v) for approximately 120 minutes.

Example 54

This example details preparation of a catalyst having a nominal Ptcontent of 2 wt. % and a nominal iron content of 4 wt. % on an activatedcarbon support having a Langmuir surface area of approximately 1500m²/g. The following preparation was conducted under nitrogen protection.

Activated carbon (approximately 10.458 g) and degassed water(approximately 90 g) were mixed in a baffled beaker under a nitrogenatmosphere.

FeCl₃.6H₂O (approximately 2.028 g) was dissolved in degassed water (20g) and this solution was pumped into the baffled beaker over a period ofapproximately 25 minutes. The pH of the slurry within the baffled beakerwas maintained at 4 by introduction of 2.5N degassed NaOH, as necessary.After addition of the FeCl₃.6H₂O solution to the beaker was completed,the pH of the slurry was raised to approximately 4.5 by addition of NaOHand the slurry was allowed to mix at ambient conditions (approximately22° C.) for approximately 10 minutes.

The slurry was then heated to a temperature of approximately 60° C. overa period of approximately 40 minutes. During the heating, the pH wasmaintained at 4.5 with addition of 2.5N degassed NaOH.

The pH of the slurry was then raised to approximately 7.5 over a periodof approximately 15 minutes at a temperature of approximately 60° C.,via increases in pH at a rate of approximately 0.5 pH units per 5minutes. The slurry was then allowed to mix at pH of approximately 7.5for approximately 10 minutes, and then cooled to ambient conditions(approximately 22° C.)

K₂PtCl₄ (approximately 0.460 g) was dissolved in degassed water(approximately 20 g) and the resulting Pt solution was then added to thebaffled beaker over a period of approximately 20 minutes. The resultingslurry was allowed to mix for approximately 30 minutes. The thus mixedslurry was then cooled to approximately 60° C. over a period of 45minutes, and then allowed to mix at 60° C. for 15 minutes.

The resulting slurry was then filtered and then dried in a vacuum ovenat approximately 110° C. for approximately 12 hours with a smallnitrogen stream to form a Pt/Fe catalyst precursor.

The catalyst precursor was then heated at elevated temperatures up toapproximately 950° C. in the presence of a hydrogen/argon stream(2%/98%; v/v) for approximately 120 minutes.

Table 25 sets forth PMIDA reaction testing results, platinum leachingdata, and iron leaching data for the 2% Pt/4% Fe finished catalyst.

TABLE 25 Cycle 1 2 3 4 5 Total CO₂ (cc) 2169.6 2196.5 2147.3 2122.52062.5 End point(min) 36.42 36.08 37.83 38.42 40.00 Maximum CO₂ 40.539.7 37.8 37.5 36.4 Concentration (%) PMIDA ND 0.008 0.008 (wt. %)Glyphosate 5.363 5.520 5.461 (wt. %) IDA(wt. %) 0.087 0.030 0.021 0.017CH₂O(ppm) 1408 1143 1247 HCOOH(ppm) 5283 5733 5993 Pt(ppm) 0.122 0.1530.155 Fe(ppm) 33.310 0.941 0.491

Example 55

This example provides microscopy results (conducted in accordance withProtocol B described in Example 68) for the catalyst precursor preparedas described in Example 54.

FIG. 116 is a scanning transmission electron microscopy (STEM)micrograph of a portion of the surface of the precursor, includingpoints 1 and 2. FIGS. 117 and 118 are results of energy dispersive x-ray(EDX) spectroscopy analysis for points 1 and 2, respectively. As shown,these portions of the precursor surface included iron well-dispersedthroughout, but not all iron had platinum deposited thereon.

FIGS. 119 and 120 are STEM photomicrographs of a portion of theprecursor surface indicating spatial distribution of metal throughoutthe carbon particle.

FIGS. 121 and 122 are an STEM micrograph and EELS line scan for aportion of the precursor surface, 1, identified in the micrograph. FIGS.123 and 124, and 125 and 126 are also pairs of STEM micrographs and EELSline scan analysis. These STEM and EELS results indicate the presence ofiron throughout the carbon particle.

Example 56

This example details preparation of a catalyst having a nominal Ptcontent of 2 wt. % and a nominal iron content of 4 wt. % on an activatedcarbon support having a Langmuir surface area of approximately 1500m²/g. The following preparation was conducted under nitrogen protection.

Activated carbon support (approximately 10.457 g) was introduced into abaffled beaker under a nitrogen atmosphere. FeCl₃.6H₂O (approximately2.013 g) and sucrose (approximately 4.550 g) were dissolved in degassedwater (approximately 85 g). 50 wt. % NaOH (approximately 5.225 g) of wasadded to and mixed with the FeCl₃.6H₂O—sucrose solution. TheFeCl₃.6H₂O—sucrose solution was then poured into the baffled beaker, andallowed to mix. The resulting slurry was then heated to approximately60° C. over a period of approximately 10 minutes.

Ethylene glycol (approximately 1.263 g) was added to the baffled beakerand allowed to mix with the slurry for approximately ten minutes atapproximately 60° C. The slurry was then filtered, and the wet cake wasthen re-slurried in the baffled beaker in degassed deionized water(approximately 90 g). The pH of the resulting slurry was then lowered toapproximately 7 by addition of degassed 2M HCl.

K₂PtCl₄ (0.462 g) was dissolved in degassed water (approximately 20 g)to form a platinum solution that was pumped into the baffled beaker overa period of approximately 20 minutes. The resulting slurry was thenallowed to mix at ambient conditions (approximately 22° C.) forapproximately 30 minutes, and then heated to a temperature ofapproximately 60° C. over a period of approximately 60 minutes. Thefinal slurry was then filtered and the wet cake was dried in a vacuumoven at approximately 110° C. for approximately 12 hours with a smallnitrogen stream to form a Pt/Fe catalyst precursor.

The catalyst precursor was then heated at elevated temperatures up toapproximately 900° C. in the presence of a hydrogen/argon stream(2%/98%; v/v) for approximately 120 minutes.

Table 26 sets forth PMIDA reaction testing results, platinum leachingdata, and iron leaching data for the 2% Pt/4% Fe catalyst.

TABLE 26 Cycle 1 2 3 4 5 6 7 8 9 10 Total CO₂ (cc) 1765.8 1812.5 1881.31908.2 1926.6 1877.7 1891.9 1878.2 1871.1 1603.1 End point(min) 44.0843.50 41.92 42.25 41.58 43.67 43.08 43.83 43.67 43.92 Maximum CO₂ 36.334.7 35.4 34.8 35.6 33.9 34.6 33.8 34.3 33.9 Concentration (%) PMIDA(wt. %) 0.005 0.009 0.010 0.009 0.011 0.074 Glyphosate(wt. %) 5.3265.397 5.348 5.448 5.423 5.568 IDA(wt. %) 0.081 0.038 0.032 0.028 0.0280.027 CH₂O(ppm) 3191 2588 2311 2559 2620 2915 HCOOH(ppm) 6079 6290 61246123 6018 6223 Pt(ppm) <0.01 0.014 0.016 0.014 0.015 0.018 Fe(ppm)55.230 3.238 0.694 0.751 0.457 0.454

Example 57

This Example details the results of microscopy analysis (conducted inaccordance with Protocol B described in Example 68) for the finishedcatalyst prepared as described in Example 56.

FIGS. 127-132 include microscopy results for the catalyst after use inPMIDA oxidation testing as described in Example 56.

FIG. 127 includes four high resolution electron photomicrographs (HREM)for various portions of the spent catalyst surface. These indicateformation of graphite and iron oxide on the outer regions of metalparticles. FIG. 128 includes three STEM micrographs, which indicate thepresence of nanoporous platinum regions.

FIG. 129 is an STEM micrograph showing various portions of the spentcatalyst surface that were analyzed by EDX analysis. The results of theEDX analysis are shown in FIG. 130, which indicates the presence of aplatinum-rich composition.

FIG. 131 is also an STEM micrograph and FIG. 132 the results of EDXanalysis for the portions of the spent catalyst surface. These resultsindicate the presence of varying metal compositions.

FIGS. 133-137 include microscopy results for the finished catalystprepared as described in Example 56, but prior to reaction testing.

FIG. 133 is an STEM photomicrograph identifying a particle to beanalyzed by EELS line scan analysis, the results of which are shown inFIG. 134. As shown in FIG. 134, a partial shell of iron oxide wasdetected.

FIG. 135 is an HREM photomicrograph highlighting Pt lattice regions. Asshown in FIG. 135, the particle identified included no more than about 4Pt lattice fringes. It is currently believed that each lattice fringecorresponds to a layer of platinum atoms. That is, the particleidentified included a layer of platinum no more than about 4 platinumatoms thick.

FIGS. 136 and 137 are HREM photomicrographs identifying two layers ofplatinum atoms.

FIG. 138 provides XRD analysis results, which indicate formation of anFe_(0.75)Pt_(0.25) phase.

Example 58

This example details preparation of a catalyst precursor having anominal Pt content of 2 wt. % and a nominal iron content of 4 wt. % onan activated carbon support having a Langmuir surface area ofapproximately 1500 m²/g. The following preparation was conducted undernitrogen protection.

Activated carbon support (approximately 10.456 g) was introduced into abaffled beaker under a nitrogen atmosphere. FeCl₃.6H₂O (approximately2.011 g) and sucrose (approximately 4.511 g) were dissolved in degassedwater (approximately 91.1 g). 50 wt. % NaOH (approximately 5.214 g) wasadded to and mixed with the FeCl₃.6H₂O—sucrose solution. TheFeCl₃.6H₂O—sucrose solution was then poured into the baffled beaker, andallowed to mix with the activated carbon support. The resulting slurrywas then heated to approximately 40° C. over a period of approximately10 minutes.

Ethylene glycol (approximately 1.309 g) was added to the baffled beakerand allowed to mix with the slurry for approximately ten minutes atapproximately 40° C. The slurry was then filtered, and the wet cake wasthen re-slurried in the baffled beaker in degassed deionized water (90g). The pH of the resulting slurry was then adjusted/lowered toapproximately 7 by addition of degassed 2M HCl (1.52 g).

K₂PtCl₄ (approximately 0.461 g) was dissolved in degassed water (20 g)to form a platinum solution that was introduced into the baffled beakerover a period of 3 minutes. The resulting slurry was then allowed to mixat approximately 25° C. for approximately 30 minutes, and then heated toa temperature of approximately 60° C. over a period of approximately 40minutes.

The final slurry was then filtered and the wet cake was washed twice bycontact with degassed water (approximately 100 g) at a temperature ofapproximately 60° C. The wet cake was dried in a vacuum oven atapproximately 110° C. for approximately 12 hours with a small nitrogenstream to form a Pt/Fe catalyst precursor.

Example 59

This example details preparation of a catalyst having a nominal Ptcontent of 2 wt. % and a nominal iron content of 4 wt. % on an activatedcarbon support having a Langmuir surface area of approximately 1500m²/g. The following preparation was conducted under nitrogen protection.

Activated carbon support (approximately 10.456 g) was introduced into abaffled beaker under a nitrogen atmosphere. FeCl₃.6H₂O (approximately2.011 g) and sucrose (approximately 4.513 g) were dissolved in degassedwater (approximately 91 g). 50 wt. % NaOH (approximately 5.25 g) wasadded to and mixed with the FeCl₃.6H₂O—sucrose solution. TheFeCl₃.6H₂O—sucrose solution was then poured into the baffled beaker, andallowed to mix with the activated carbon support.

Ethylene glycol (approximately 1.31 g) was added to the baffled beakerand the resulting slurry was heated to a temperature of approximately30° C. over a period of approximately 15 minutes. The slurry was thenfiltered, and the wet cake was then re-slurried in the baffled beaker incold degassed deionized water (90 g) at a temperature of approximately12° C. The pH of the resulting solution was then lowered toapproximately 7 by addition of degassed 2M HCl (approximately 0.645 g)and 1M HCl (approximately 0.461 g).

K₂PtCl₄ (approximately 0.461 g) was dissolved in cold degassed water(approximately 20 g) at a temperature of approximately 12° C. Theplatinum solution was then pumped into the baffled beaker over a periodof approximately 20 minutes.

The final slurry was then filtered and the wet cake was dried in avacuum oven at approximately 110° C. for approximately 12 hours with asmall nitrogen stream to form a Pt/Fe catalyst precursor.

The catalyst precursor was then heated at elevated temperatures up toapproximately 755° C. in the presence of a hydrogen/argon stream(4%/96%; v/v) for approximately 120 minutes.

Table 27 sets forth PMIDA reaction testing results, platinum leachingdata, and iron leaching data for the 2% Pt/4% Fe finished catalyst.

TABLE 27 Cycle 1 2 3 4 5 6 7 8 9 10 Total CO₂ (cc) 1776.6 1830.6 1877.31898.8 1846.8 1868.2 1853.1 1825.1 1827.8 1600.2 End point(min) 44.7544.92 43.67 44.00 46.25 45.75 46.25 47.42 47.00 48.50 Maximum CO₂ 35.633.5 33.7 33.7 32.5 32.8 32.6 32.0 32.7 31.7 Concentration (%) PMIDA(wt. %) ND 0.003 0.005 0.004 0.006 0.057 Glyphosate(wt. %) 5.278 5.4635.489 5.450 5.508 5.516 IDA(wt. %) 0.079 0.036 0.031 0.029 0.029 0.029CH₂O(ppm) 3702 2914 2366 2434 2422 2756 HCOOH(ppm) 5549 6036 5987 58825850 5842 Pt(ppm) 0.016 0.016 0.018 0.019 0.017 0.017 0.022 Fe(ppm)36.130 11.570 2.818 0.552 0.456 0.423 0.375

Example 60

FIGS. 139-148 include microscopy results (conducted in accordance withProtocol B described in Example 68) for the finished catalyst preparedas described in Example 59.

FIG. 139 is an STEM micrograph identifying the particle analyzed by EELSline scan analysis, the results of which are shown in FIG. 140. As shownin FIG. 139, the Fe:Pt atomic ratio of the particle analyzed was85.99/14.01. The line scan results of FIG. 140 indicate formation of aniron oxide outer layer.

FIG. 141 is an STEM micrograph indicating the particle that was analyzedby EDX line scan analysis, the results of which are shown in FIG. 142.The line scan results indicate a relatively constant platinum signal,suggesting a very thin platinum shell, i.e., varying by no more thanabout 25% during the scan across the particle (e.g., from about 17.5 nmto about 46 nm along the scanning line. As also shown in FIG. 142, thevariation in the magnitude of the iron signal during the scan across theparticle is proportionally greater than the variation in the platinumsignal during the scan across the particle (i.e., on the order of atleast about 1.5:1).

FIG. 143 is an STEM micrograph and FIGS. 144 and 145 the correspondingEELS line scan analysis and EDX line scan analysis, respectively. TheEELS line scan results indicate the presence of an iron oxide layer. TheEDX line scan results indicate the presence of a thin platinum shell.

FIG. 146 is an STEM micrograph and FIG. 147 the corresponding EDX linescan analysis. The line scan results indicate a relatively constantplatinum signal, i.e., ranging by no more than about 25% during the scanacross the particle from about 9 nm to about 35 nm along the scanningline and a greater variation in the magnitude of the iron signal ascompared to the variation in the platinum signal (i.e., on the order ofabout 1.5:1).

FIG. 148 provides XRD results of analysis conducted as described inExample 69. These results indicate formation of an Fe_(0.75)Fe_(0.25)phase.

FIGS. 149-153 are microscopy results for the spent catalyst (i.e., aftertesting in PMIDA oxidation).

FIG. 149 is an STEM micrograph showing various porous metal particles atthe spent catalyst surface.

FIG. 150 is an STEM micrograph and FIG. 151 the corresponding EDX linescan analysis results. FIG. 152 is an STEM micrograph and FIG. 153 thecorresponding EDX line scan analysis results. These results indicate aplatinum-rich composition throughout the particles analyzed due toleaching of iron from the core, i.e., inner regions of the particles toform porous platinum-rich particles.

Example 61

This example details preparation of a catalyst precursor having anominal Pt content of 2 wt. % and a nominal iron content of 3.5 wt. % onan activated carbon support having a Langmuir surface area ofapproximately 1500 m²/g. The following preparation was conducted undernitrogen protection.

Activated carbon support (approximately 10.457 g) was introduced into abaffled beaker under a nitrogen atmosphere. FeCl₃.6H₂O (approximately1.753 g) and sucrose (approximately 4.455 g) were dissolved in degassedwater (approximately 90 g). 50 wt. % NaOH (approximately 4.613 g) wasadded to and mixed with the FeCl₃.6H₂O—sucrose solution. TheFeCl₃.6H₂O—sucrose solution was then poured into the baffled beaker, andallowed to mix with the activated carbon support. The slurry was thenheated a temperature of approximately 60° C. over a period of 10minutes.

Ethylene glycol (approximately 1.200 g) was added to the baffled beakerand allowed to mix with the slurry for approximately ten minutes atapproximately 60° C. The slurry was then filtered, and the wet cake wasthen re-slurried in degassed deionized water (90 g) and introduced intothe baffled beaker. The pH of the resulting slurry was then lowered toapproximately 6 by addition of degassed 1M HCl (3.6 g).

K₂PtCl₄ (approximately 0.452 g) was dissolved in degassed water(approximately 20 g) to form a platinum solution that was introducedinto the baffled beaker over a period of approximately 3 minutes. Theresulting slurry was then allowed to mix at ambient conditions(approximately 22° C.) for approximately 15 minutes, and then heated toa temperature of approximately 40° C. over a period of approximately 12minutes.

The final slurry was then filtered and the wet cake was hot washed twiceby contact with degassed water (approximately 100 g) at a temperature ofapproximately 60° C. The resulting sample was then dried in a vacuumoven at approximately 110° C. for approximately 12 hours with a smallnitrogen stream.

The catalyst precursor was then heated at elevated temperatures up toapproximately 755° C. in the presence of a hydrogen/argon stream(4%/96%; v/v) for approximately 120 minutes.

FIG. 154 provides XRD analysis results for the finished 2% Pt/3.5% Fecatalyst, which indicate formation of a Fe₃Pt phase.

Table 28 sets forth PMIDA reaction testing results, platinum leachingdata, and iron leaching data for the finished catalyst. FIG. 155provides XRD analysis results for the catalyst after reaction testing(i.e., the spent catalyst). These results indicate formation of a Ptphase.

TABLE 28 Cycle 1 2 3 4 5 6 7 8 9 10 Total CO₂ (cc) 1785.7 1841.8 1913.61928.1 1970.6 1956.8 1956.0 1947.8 1967.6 1602.0 End point(min) 43.8341.67 39.83 40.17 40.42 40.75 40.58 41.83 41.67 42.75 Maximum CO₂ 35.436.0 36.9 36.9 36.2 35.7 36.2 35.1 35.4 34.7 Concentration (%) PMIDA(wt. %) ND 0.003 0.004 0.004 0.004 0.143 Glyphosate(wt. %) 5.169 5.4055.405 5.343 5.446 5.430 IDA(wt. %) 0.085 0.045 0.039 0.038 0.036 0.036CH₂O(ppm) 3172 2624 2341 2272 2068 2612 HCOOH(ppm) 6258 6539 6489 63916313 6465 Pt(ppm) 0.011 0.013 0.014 0.016 0.016 0.022 Fe(ppm) 24.6802.502 0.584 0.487 0.363 0.362

Example 61A

This example details preparation of a catalyst having a nominal Ptcontent of 2 wt. % and a nominal iron content of 4 wt. % on an activatedcarbon support having a Langmuir surface area of approximately 1500m²/g. The following preparation was conducted under nitrogen protection.

Activated carbon (approximately 10.456 g) and degassed water(approximately 90 g) were mixed in a baffled beaker and allowed to mixfor 20 minutes.

FeCl₃.6H₂O (approx. 2.009 g) was dissolved in degassed water (40 g) andthis solution was then pumped into the baffled beaker over a period of30 minutes while maintaining the pH of the slurry at 4 with 2.5N NaOH,as necessary. After addition of the FeCl₃.6H₂O solution to the beakerwas completed, the pH of the slurry was raised to 4.5 and allowed to mixfor 10 minutes.

The slurry was then heated to approximately 60° C. over a period ofapproximately 30 minutes. During the heating, the pH was maintained at4.5. The pH of the slurry was then raised to 11 over a period of 30minutes, and then allowed to mix for 10 minutes. Ethylene glycol (1.388g) was then added to the slurry, and allowed to mix at approximately 60°C. for approximately 10 minutes. The slurry was then filtered, and thewet cake was then re-slurried in the baffled in degassed deionized water(approx. 90 g).

The pH of the solution was then lowered to 7 by addition of 0.5Mdegassed HCl. K₂PtCl₄ (0.460 g) was dissolved in 20 mL of degassedwater. The Pt solution was then pumped into the baffled beaker over aperiod of 30 minutes. The resulting slurry was then allowed to mix atambient conditions (approx. 20 ° C.) for approximately 30 minutes, andthen heated to a temperature of approximately 60° C. over a period of 10minutes.

The resulting slurry was then filtered and washed twice by contact withdegassed water (approx. 100 g) at a temperature of approximately 60° C.The sample was then dried in a vacuum oven at approximately 110° C. for12 hours with a small nitrogen stream to form a Pt/Fe catalystprecursor.

The catalyst precursor was then heated at elevated temperatures up toapproximately 650° C. in the presence of a hydrogen/argon stream(4%/96%; v/v) for approximately 120 minutes.

V. Platinum-Cobalt

Example 62

This example details preparation of a catalyst having a nominal platinumcontent of approximately 2 wt. % and a nominal cobalt content ofapproximately 4 wt. % on an activated carbon support having a Langmuirsurface area of approximately 1500 m²/g. The following preparation wasconducted under nitrogen protection.

CoCl₂ (1.686 g) and sucrose (4.499 g) were dissolved in degassed water(89.4 mL) in a screw top jar that had been flushed with nitrogen. Tothis mixture was added 50 wt. % sodium hydroxide (5.209 g), the jar wasflushed with nitrogen, and the solution was then mixed for one minute.

Activated carbon support (10.458 g) was added to a 400 mL baffled beakerand the CoCl₂ solution was then poured into the baffled beaker, thebeaker was flushed with nitrogen, and the components were allowed to mixat room temperature for approximately five minutes. The resultingsolution was then heated to approximately 60° C. over a period ofapproximately forty minutes. Ethylene glycol (approx. 1.272 g) was thenadded, and the resulting solution was allowed to mix at approximately60° C. for approximately twenty minutes.

The solution was then filtered on a fritted glass filter, the resultingwet cake was returned to the baffled beaker. The pH of the solution wasreduced to approximately 4.7 by addition of HCl (2M).

K₂PtCl₄ (approx. 0.460 g) was dissolved in degassed water (20 ml) andthe platinum solution was added to the baffled beaker drop-wise over aperiod of approximately three minutes. The resulting solution wasallowed to mix at approximately 25° C. for approximately sixty minutes.The solution was then heated to approximately 60° C. over a period ofapproximately twenty minutes. The resulting solution was then filtered,and the filtrate was hot washed twice with in degassed water (120 ml) atapproximately 60° C. The sample was then dried in a vacuum oven at 110°C. for 12 hours with a nitrogen stream.

The catalyst precursor was then heated at elevated temperatures up toapproximately 900° C. in the presence of a hydrogen/argon stream(4%/96%; v/v) for approximately 120 minutes.

Example 63

This example details preparation of a catalyst precursor having anominal platinum content of 2 wt. % and a cobalt content of 4 wt. % onan activated carbon support having a Langmuir surface area ofapproximately 1500 m²/g. The following preparation was conducted undernitrogen protection.

Activated carbon (10.458 g) was placed in a baffled beaker. CoCl₂.6H₂O(1.685 g) and sucrose (4.566 g) were mixed with degassed water (89.2 ml)and allowed to dissolve. 5.154 g of 50 wt. % sodium hydroxide was addedto the cobalt solution and allowed to mix. The resulting CoCl₂.6H₂Osolution was then poured into the baffled beaker with carbon, andallowed to mix.

The resulting slurry was then heated to approximately 60° C. over aperiod of twenty minutes. Sodium borohydride (approx. 0.558 g) wasdissolved in degassed water (20 ml) to which 2.5N degassed NaOH (0.329g) was then added. The sodium borohydride solution was added to thebaffled beaker at approximately 60° C. over a period of approximatelytwenty minutes, and then allowed to mix for ten additional minutes. Theslurry was then filtered, and the wet cake was washed twice atapproximately 60° C. The resulting wet cake was then re-slurried indegassed deionized water (90 g).

The pH of the solution was reduced to approximately 5 by addition ofdegassed 2M HCl. K₂PtCl₄ (0.459 g) was dissolved in degassed water (20ml). The Pt solution was then added to the baffled beaker over a periodof approximately three minutes. The slurry was then allowed to mix atapproximately 25° C. for approximately 40 minutes, and then heated to atemperature of approximately 40° C.

The resulting slurry was then filtered, and the wet cake was washedtwice with hot water (approx. 100 ml) at approx. 60° C. The resultingsample was then dried in a vacuum oven at approximately 110° C. for 12hours with a small nitrogen stream.

VI. Platinum-Tin

Example 64

The following preparation was conducted under nitrogen protection.Activated carbon (10.457 g) was placed in a baffled beaker and mixedwith degassed water (100 ml).

SnCl₄.5H₂O (2.545 g) and K₂PtCl₄ (0.463 g) were dissolved in degassedwater (20 ml). The Sn/Pt solution was then pumped into the baffledbeaker over a period of approximately twenty-three minutes. Thetemperature and pH of the Sn/Pt solution were raised simultaneously toapproximately 60° C. and approximately 7, respectively, over a period ofapproximately forty five minutes. The solution was allowed to mix forapproximately thirty minutes.

NaBH₄ (1.310 g) was dissolved in degassed water (10 ml) and thissolution was added to the baffled beaker over a twenty minute period.The resulting slurry was then allowed to mix for approximately twentyminutes, the slurry filtered, and the wet cake was hot washed twice withapproximately 100 ml of degassed water at approximately 60° C. Theresulting sample was then dried in a vacuum oven at 110° C. for 12 hourswith a small nitrogen stream.

The catalyst precursor was then heated at elevated temperatures up toapproximately 545° C. in the presence of a hydrogen/argon stream(2%/98%; v/v) for approximately 120 minutes.

VII. Platinum-Copper

Example 65

The following preparation was conducted under nitrogen protection.

Preparation of nominal 2% Pt4% Cu on activated carbon: The following wasadded to a baffled beaker including approx. 10 g of activated carbon:1.64 g of CuSO₄.5H₂O solution, 4.51 g of sucrose, 90 g of degasseddeionized water, and 4.63 g of 50 wt. % NaOH. The mixture was heated toapprox. 40° C. and stirred for approx. 10 minutes with a mechanicalagitator. To this slurry was added 1.71 g of 37% formaldehyde diluted to17.1 g with degassed deionized water. The resulting slurry was heated toapprox. 40° C. along with continued stirring for approx. 30 minutes (oruntil solution became colorless). Then the slurry was filtered, washedonce in the filter, and then re-slurried in water to pH 2.02 by adding1M degassed HCl. A solution of 0.454 g of K₂PtCl₄ in 10 g of degassedwater was then added to the slurry, along with continued stirring forapprox. 30 minutes at ambient conditions. Then the slurry was heated toapprox. 60° C. and stirred for approx. 30 more minutes. This slurry wasthen filtered and washed with water, and dried under vacuum at approx.110° C. under a small stream of nitrogen. A total of 11.720 g of driedmaterial was recovered. During heat treatment to a maximum temperatureof approximately 950° C. in the presence of an argon/hydrogen atmosphere(2%/98%) (v/v) for approximately 120 minutes, the sample lost 13.5%weight.

FIGS. 155A and 155B include microscopy results for the finishedcatalyst. FIGS. 155C-155F include microscopy results for the catalystafter testing in PMIDA oxidation.

Example 66

This example details preparation of a catalyst having a nominal Ptcontent of 2 wt. % and a nominal copper content of 3.75 wt. % on anactivated carbon support having a Langmuir surface area of approximately1500 m²/g. The following preparation was conducted under nitrogenprotection.

Activated carbon support (approximately 10.457 g) was introduced into abaffled beaker under a nitrogen atmosphere. CuSO₄.5H₂O (approximately1.540 g) and sucrose (approximately 4.225 g) were dissolved in degassedwater (approximately 91 g). 50 wt. % NaOH (approximately 4.370 g) wasadded to and mixed with the CuSO₄.5H₂O—sucrose solution, and theresulting solution was then poured into the baffled beaker, and allowedto mix with the activated carbon support at a temperature ofapproximately 29° C. for approximately 20 minutes.

Formaldehyde (37%) (approximately 1.604 g) was added to the baffledbeaker and allowed to mix with the slurry for approximately eighty fourminutes at approximately 29° C. The slurry was then filtered, and thewet cake was then re-slurried in degassed deionized water (90 g) andintroduced into the beaker. The pH of the resulting slurry was thenlowered to approximately 4 by addition of degassed 1M HCl.

K₂PtCl₄ (approximately 0.427 g) was dissolved in degassed water(approximately 20 g) to form a platinum solution that was introducedinto the baffled beaker over a period of approximately 3 minutes. Theresulting slurry was then allowed to mix at ambient conditions(approximately 22° C.) for approximately 30 minutes, and then heated toa temperature of approximately 60° C., and then mixed for approximatelyan additional 30 minutes.

The final slurry was then filtered and the wet cake was hot washed twiceat 60° C. by contact with degassed water (approximately 100 g). Theresulting sample was dried in a vacuum oven at approximately 110° C. forapproximately 12 hours with a small nitrogen stream.

The catalyst precursor was then heated at elevated temperatures up toapproximately 950° C. in the presence of a hydrogen/argon stream(2%/98%; v/v) for approximately 120 minutes.

Table 29 sets forth PMIDA reaction testing results, platinum leachingdata, and iron leaching data for the finished catalyst.

TABLE 29 Cycle 1 2 3 4 5 6 7 8 9 10 Total CO₂ (cc) 1916.9 2049.0 2048.72037.5 2010.9 1996.5 1995.9 1918.9 1920.4 1601.5 End point(min) 49.0043.50 42.00 42.17 42.33 42.33 41.58 44.42 44.92 45.07 Maximum CO₂ 29.832.6 33.7 33.9 34.6 34.9 36.9 33.9 33.8 33.9 Concentration (%) PMIDA(wt. %) 0.007 0.004 0.006 0.005 0.005 0.217 Glyphosate(wt. %) 5.4765.553 5.492 5.511 5.474 5.443 IDA(wt. %) 0.051 0.021 0.018 0.019 0.0190.018 CH₂O(ppm) 2208 2057 1905 2105 1876 2517 HCOOH(ppm) 4743 4945 52345567 5780 5802 Pt(ppm) 0.023 0.031 0.033 0.039 0.046 0.068 Fe(ppm)16.930 0.953 0.553 0.387 0.284 0.247VIII. Testing Protocols

Example 67 Protocol A

The following example details CO chemisorption analysis used todetermine the exposed metal surface areas of catalysts prepared asdescribed herein. The method described in this example is referenced inthis specification and appended claims as “Protocol A.”

This protocol subjects a single sample to two sequential COchemisorption cycles.

Cycle 1 measures initial exposed noble metal at zero valence state. Thesample is vacuum degassed and treated with oxygen. Next, residual,un-adsorbed oxygen is removed and the catalyst is then exposed to CO.The volume of CO taken up irreversibly is used to calculate initialnoble metal (e.g., Pt⁰) site density.

Cycle 2 measures total exposed noble metal. Without disturbing thesample after cycle 1, it is again vacuum degassed and then treated withflowing hydrogen, and again degassed. Next the sample is treated withoxygen. Finally, residual, non-adsorbed oxygen is removed and thecatalyst is then again exposed to CO. The volume of CO taken upirreversibly is used to calculate total exposed noble metal (e.g., Pt⁰)site density. See, for example, Webb et al., Analytical Methods in FineParticle Technology, Micromeritics Instrument Corp., 1997, for adescription of chemisoprtion analysis. Sample preparation, includingdegassing, is described, for example, at pages 129-130.

Equipment:

Micromeritics (Norcross, Ga.) ASAP 2010˜ static chemisorptioninstrument; Required gases: UHP hydrogen; carbon monoxide; UHP helium;oxygen (99.998%); Quartz flow through sample tube with filler rod; twostoppers; two quartz wool plugs; Analytical balance.

Preparation:

Insert quartz wool plug loosely into bottom of sample tube. Obtain tareweight of sample tube with 1st wool plug. Pre-weigh approximately 0.25grams of sample then add this on top of the 1st quartz wool plug.Precisely measure initial sample weight. Insert 2nd quartz wool plugabove sample and gently press down to contact sample mass, then addfiller rod and insert two stoppers. Measure total weight (before degas):Transfer sample tube to degas port of instrument then vacuum to <10 μmHg while heating under vacuum to 150° C. for approximately 8-12 hours.Release vacuum. Cool to ambient temperature and reweigh. Calculateweight loss and final degassed weight (use this weight in calculations).

Cycle 1:

Secure sample tube on analysis port of static chemisorption instrument.Flow helium (approximately 85 cm³/minute) at ambient temperature andatmospheric pressure through sample tube, then heat to 150° C. at 5°C./minute. Hold at 150° C. for 30 minutes. Cool to 30° C.

Evacuate sample tube to <10 μm Hg at 30° C. Hold at 30° C. for 15minutes. Close sample tube to vacuum pump and run leak test. Evacuatesample tube while heating to 70° C. at 5° C./min. Hold for 20 minutes at70° C.

Flow oxygen (approximately 75 cm³/minute) through sample tube at 70° C.and atmospheric pressure for 50 minutes.

Evacuate sample tube at 70° C. for 5 minutes.

Flow helium (approximately 85 cm³/minute) through sample tube atatmospheric pressure and increase to 80° C. at 5° C./minute. Hold at 80°C. for 15 minutes.

Evacuate sample tube at 80° C. for 60 minutes and hold under vacuum at80° C. for 60 minutes. Cool sample tube to 30° C. and continueevacuation at 30° C. for 30 minutes. Close sample tube to vacuum pumpand run leak test.

Evacuate sample tube at 30° C. for 30 minutes and hold under vacuum at30° C. for 30 minutes.

For a first CO analysis, CO uptakes are measured under staticchemisorption conditions at 30° C. and starting manifold pressures of50, 100, 150, 200, 250, 300, 350 and 400 mm Hg (gauge) to determine thetotal amount of CO adsorbed (i.e., both chemisorbed and physisorbed).

Pressurize manifold to the starting pressure (e.g., 50 mm Hg). Openvalve between manifold and sample tube allowing CO to contact the samplein the sample tube. Allow the pressure in the sample tube toequilibrate. The reduction in pressure from the starting manifoldpressure to equilibrium pressure in the sample tube indicates the volumeof CO uptake by the sample.

Close valve between the manifold and sample tube and pressurize themanifold to the next starting pressure (e.g., 100 mm Hg). Open valvebetween manifold and sample tube allowing CO to contact the sample inthe sample tube. Allow the pressure in the sample tube to equilibrate todetermine the volume of CO uptake by the sample. Perform for eachstarting manifold pressure.

Evacuate sample tube at 30° C. for 30 minutes.

For a second CO analysis, CO uptakes are measured under staticchemisorption conditions at 30° C. and starting manifold pressures of50, 100, 150, 200, 250, 300, 350 and 400 mm Hg (gauge) as describedabove for the first CO analysis to determine the total amount of COphysisorbed.

Cycle 2:

After the second CO analysis of Cycle 1, flow helium (approximately 85cm³/minute) at 30° C. and atmospheric pressure through sample tube thenheat to 150° C. at 5° C./minute. Hold at 150° C. for 30 minutes.

Cool to 30° C. Evacuate sample tube to <10 μm Hg at 30° C. for 15minutes. Hold at 30° C. for 15 minutes.

Close sample tube to vacuum pump and run leak test.

Evacuate sample tube at 30° C. for 20 minutes.

Flow hydrogen (approximately 150 cm³/minute) through sample tube atatmospheric pressure while heating to 150° C. at 10° C./min. Hold at150° C. for 15 minutes.

Evacuate sample tube at 150° C. for 60 minutes. Cool sample tube to 70°C. Hold at 70° C. for 15 minutes.

Flow oxygen (approximately 75 cm³/minute) through sample tube atatmospheric pressure and 70° C. for 50 minutes.

Evacuate sample tube at 70° C. for 5 minutes.

Flow helium (approximately 85 cm³/minute) through sample tube atatmospheric pressure and increase temperature to 80° C. at 5° C./minute.Hold at 80° C. for 15 minutes. Evacuate sample tube at 80° C. for 60minutes. Hold under vacuum at 80° C. for 60 minutes.

Cool sample tube to 30° C. and continue evacuation at 30° C. for 30minutes. Close sample tube to vacuum pump and run leak test.

Evacuate sample tube at 30° C. for 30 minutes and hold for 30 minutes.

For a first CO analysis, CO uptakes are measured under staticchemisorption conditions at 30° C. and starting manifold pressures of50, 100, 150, 200, 250, 300, 350 and 400 mm Hg (gauge) to determine thetotal amount of CO adsorbed (i.e., both chemisorbed and physisorbed).

Pressurize manifold to the starting pressure (e.g., 50 mm Hg). Openvalve between manifold and sample tube allowing CO to contact the samplein the sample tube. Allow the pressure in the sample tube toequilibrate. The reduction in pressure from the starting manifoldpressure to equilibrium pressure in the sample tube indicates the volumeof CO uptake by the sample.

Close valve between the manifold and sample tube and pressurize themanifold to the next starting pressure (e.g., 100 mm Hg). Open valvebetween manifold and sample tube allowing CO to contact the sample inthe sample tube. Allow the pressure in the sample tube to equilibrate todetermine the volume of CO uptake by the sample. Perform for eachstarting manifold pressure.

Evacuate sample tube at 30° C. for 30 minutes.

For a second CO analysis, CO uptakes are measured under staticchemisorption conditions at 30° C. and starting manifold pressures of50, 100, 150, 200, 250, 300, 350 and 400 mm Hg (gauge) as describedabove for the first CO analysis to determine the total amount of COphysisorbed.

Calculations:

Plot first and second analysis lines in each cycle: volume CO physicallyadsorbed and chemisorbed (1st analysis) and volume CO physicallyadsorbed (2nd analysis) (cm³/g at STP) versus target CO pressures (mmHg). Plot the difference between First and Second analysis lines at eachtarget CO pressure. Extrapolate the difference line to its interceptwith the Y-axis. In Cycle 1, total exposed Pt₀ (μmole CO/g)=Y-interceptof difference line/22.414×1000. In Cycle 2, total exposed Pt (μmoleCO/g)=Y-intercept of difference line/22.414×1000.

Example 68 (Microscopy): Protocol B

This Example details microscopy analysis of catalyst samples of thepresent invention.

High Resolution Electron Micrographs (HREM):

HREM for various catalyst samples were generated using a Jeol 2100 fieldemission gun (FEG) transmission electron microscope (TEM) operated at anaccelerating voltage of 200 keV. Samples were placed in the holder as-iswithout carbon interference (i.e., the samples were not microtomed andembedded in an organic-containing material such as an epoxy), and underconditions that identified lattice fringe rings.

Atomic Layer Measurements:

Lattice d spacings of catalyst particles identified by TEM weremeasured. These measurements were calibrated based on the known dspacing (3.84 A) of single crystal silicon (110) that was also analyzedusing the Jeol 2100 FEG TEM at the same magnification and acceleratingvoltage (200 KeV). The measurements were recorded and analyzed usingDigitalMicrograph software. The number of atomic layers of platinum forthe particles analyzed was determined based from the number of repeatinglattice fringe rings observed in the HREM micrographs.

Line Scan Analysis:

Energy dispersive x-ray spectroscopy (EDX) line scan analysis wasconducted using the Jeol 2100 FEG TEM operated in scanning transmissionelectron microscopy (STEM) mode. The probe size was 1 nm.

Electron energy loss spectroscopy (EELS) line scan analysis wasconducted using the Jeol 2100 FEG TEM operated in STEM mode with a probesize of 0.5 nm.

Example 69 X-Ray Diffraction

This example details the method utilized for X-Ray Diffraction (XRD)analysis for the results reported herein. Powder samples (less thanapprox. 0.2 g) were compacted using a pellet press to form samplepellets for analysis. The sample pellet was placed on a plastic sampleholder for analysis in a Bruker D8 Discover Diffractometer.

CuK∝X radiation (λ_(CuK∝)=1.5418 Å) was produced in a sealed Cu tube at40 kV and 40 mA. Prior to the experiment, a korundum sample was used toadjust any peak misalignments.

The sample holder was placed on the XYZ stage and analyzed in lockedcoupled scan mode; the gun and detector angles were kept at the samevalue (i.e., θ₁=θ₂). XRD data were collected using a LynxEye® PositionSensitive Detector (PSD) which is 10³ times more sensitive than regularXRD. For each sample, an XRD spectrum was collected within the 0-90° 2θrange with a step size of 0.02° and a total collection time of approx. 3hours.

Example 70 Pore Volume and Surface Area Analysis

Various metal-impregnated supports and catalysts were generally analyzedto determine surface area and pore volume data as reported herein usinga Micromeritics 2010 Micropore analyzer with a one-torr transducer and aMicromeritics 2020 Accelerated Surface Area and Porosimetry System, alsowith a one-torr transducer. These analysis methods are described in, forexample, Analytical Methods in fine Particle Technology, First Edition,1997, Micromeritics Instrument Corp.; Atlanta, Ga. (USA); and Principlesand Practice of Heterogeneous Catalysis, 1997, VCH Publishers, Inc; NewYork, N.Y. (USA).

The present invention is not limited to the above embodiments and can bevariously modified. The above description of the preferred embodiments,including the Examples, is intended only to acquaint others skilled inthe art with the invention, its principles, and its practicalapplication so that others skilled in the art may adapt and apply theinvention in its numerous forms, as may be best suited to therequirements of a particular use.

With reference to the use of the word(s) comprise or comprises orcomprising in this entire specification (including the claims below),unless the context requires otherwise, those words are used on the basisand clear understanding that they are to be interpreted inclusively,rather than exclusively, and applicants intend each of those words to beso interpreted in construing this entire specification.

When introducing elements of the present invention or the preferredembodiments(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

What is claimed is:
 1. A process for oxidizing a substrate selected fromthe group consisting of N-(phosphonomethyl)iminodiacetic acid or a saltthereof, formaldehyde, and formic acid, the process comprising:contacting the substrate with an oxidizing agent in the presence of anoxidation catalyst comprising a particulate carbon support, a firstmetal, and a second metal, the support having at its surface particlescomprising the first metal and the second metal, wherein: the firstmetal constitutes from about 1% to about 10% by weight of the catalyst;the first metal is selected from the group consisting of copper, tin,nickel, cobalt, and combinations thereof; the second metal constitutesfrom about 1% to about 6% by weight of the catalyst; the second metal isselected from the group consisting of platinum, palladium, ruthenium,rhodium, iridium, silver, osmium, gold, and combinations thereof; thecarbon support has a specific surface area of at least about 500 m²/g;and wherein first metal and second metal-containing particles at thesurface of the carbon support comprise a core comprising the first metaland a shell at least partially surrounding the core and comprisingsecond metal, the shell having a thickness of no more than five secondmetal atoms.
 2. The process as set forth in claim 1 wherein the shellhas a thickness of no more than 3 second metal atoms.
 3. The process asset forth in claim 1 wherein the shell has a thickness of no more than 2second metal atoms.
 4. The process as set forth in claim 1 wherein thefirst metal constitutes from about 2% to about 5% by weight of thecatalyst.
 5. The process as set forth in claim 1 wherein the secondmetal constitutes from about 1% to about 5% by weight of the catalyst.6. The process as set forth in claim 1 wherein the first metal iscopper.
 7. The process as set forth in claim 1 wherein the first metalis iron.
 8. The process as set forth in claim 1 wherein the first metalis cobalt.
 9. The process as set forth in claim 1 wherein the secondmetal is platinum.
 10. The process as set forth in claim 1 wherein atleast about 10% of the second metal is present within the shell of themetal particles.
 11. The process as set forth in claim 1 wherein theatom percent of second metal at the surface of first metal and secondmetal-containing particles at the surface of the carbon support is atleast about 2%.
 12. The process as set forth in claim 1 wherein theatomic ratio of second metal to first metal of the at least one particleis less than 1:1.
 13. The process as set forth in claim 1 wherein the atleast one particle has a largest dimension of at least about 6 nm. 14.The process as set forth in claim 1 wherein the at least one particleconstitutes at least about 1% of the metal particles at the surface ofthe carbon support.
 15. The process as set forth in claim 1 wherein thecarbon support has a specific surface area from about 500 m²/g to about1900 m²/g.